Government & Advisory Services
Strategic property advice for local, regional, and national government agencies.
Make critical decisions that contribute to the success of your investments and your organisation with our leading government property advisory services. Whether you’re a local, regional or national government agency– we have the expertise and technology to ensure high-quality advice and reports to empower more informed property decisions.

Our Coverage
We have a specialised team of professional valuers who handle government property services with unmatched knowledge and expertise to support your property decisions.

Our Technology
Our technology enhances the valuation process for everyone involved with customisable, automated workflows and centralised systems to access, manage, and deliver your reports.

Our Process
Opteon works with a vast range of Central, Regional & Local Government departments & their agencies.
Government Advisory Services
We provide a range of property advisory services with individualised solutions and expertise. Our advisors are skilled at analysing the local property markets, understanding various market sectors – from residential to rural –, and providing strategic property and risk management advice for a range of government departments and agencies.
Rating Valuations
We are proud to be the Valuation Service Providers (VSP) for several Councils in New Zealand, providing our customers with market-leading valuation management platforms to enable business decisions through the utilisation of technology.
Financial Reporting for Local Governments
Make critical decisions that contribute to the success of your investments and your organisation with our leading government property advisory services.
Rating Valuations
We are proud to be the Valuation Service Providers (VSP) for several Councils in New Zealand, providing our customers with market-leading valuation management platforms to enable business decisions through the utilisation of technology.
Financial Reporting for Local Governments
Make critical decisions that contribute to the success of your investments and your organisation with our leading government property advisory services.
Get In Touch with an Expert

Avella Taylor
Regional Director

Ashton Gibbard
Associate Director

Joe Holmes
Associate Director

Ben Williams
Valuer

Ewen Lilburn
Appointee Valuer

Lionel Musson
Registered Valuer

Mark Grinlinton
Registered Valuer

Martyn Oostveen
Senior Rural Valuer

Mate Finlay
Valuer

Shelley Manson
Valuer

Tom Mabbott
Registered Valuer

Avella Taylor
Formal Qualifications
- Registered Valuer in New Zealand (Member No. NZIV 3780)
- Member of the Property Institute New Zealand
- Property Institute of New Zealand Branch Committee Chair – Auckland
- Bachelor of Commerce (Property Valuation) - Curtin University of Technology Western Australia 2014
Industry Experience
Avella has several years’ experience as a valuer and has been employed by Opteon since 2013. She is the Regional Director of Government Services for New Zealand and leads the Government Department which undertakes valuations throughout New Zealand.
Areas of Expertise
- Valuations for mortgage purposes
- Residential valuations
- Asset valuations for financial reporting and insurance purposes
- Project management and delivery

Ashton Gibbard
Formal Qualifications
- Registered Property Valuer
- Bachelor of Business Studies (Valuation and Property Management)
Industry Experience
Ashton has been valuing since 2011 and has a wide knowledge base with experience across valuation sectors including rating valuations (roll maintenance and revaluations), financial reporting valuations, project managing national portfolio valuations, along with private market and insurance valuations. Ashton has worked on rating contracts throughout the lower and central North Island and across the Northland Region.
Areas of Expertise
- Multi-unit residential investment property valuation
- Valuations of development and block land
- Valuation of specialist property under depreciated replacement cost methodology
- Mass Appraisal Valuation techniques for revaluations
- Financial Reporting and Asset Valuations and Reporting
- Legislation, requirements and procedures for rating valuations
- Procedural and reporting for Land Valuation Tribunal

Joe Holmes
Formal Qualifications
- Certified Practising Valuer
- Associate Member of the Australian Property Institute (API Member No. 82770)
- Registered Valuer (NZIV, MPINZ) (Registration Certificate No. 3942)
- Land Valuers Licence (Western Australia) (Licence No. LV45100)
- Bachelor of Applied Science (Property and Valuation) (1st Class Honours)
Industry Experience
Joe is an experienced rating and taxing valuer having commenced his career in Melbourne undertaking a range of valuations for municipalities including Manningham City Council, Kingston City Council, Glen Eira City Council, Frankston City Council, Yarra City Council, Moreland City Council, Mornington Shire and more. He has vast experience returning annual general revaluations, objections, supplementary valuations, public open space contribution valuations, asset valuations, rental determinations and insurance valuations covering a range of property types such as commercial, industrial, residential, and specialist. In 2020 he migrated home to Auckland (New Zealand) and in 2021 joined Opteon as an Associate Director in their Government and Advisory team. He is a Registered Valuer in New Zealand, Certified Practising Valuer in Victoria, and holds a Land Valuers Licence in Western Australia.
Areas of Expertise
- Valuations for property taxation, legislation and policy purposes
- Mass valuation modelling
- Rating and taxing valuations
- Rating and Land Tax objections
- Asset valuations for financial reporting purposes
- Public open space contribution valuations

Ben Williams
Formal Qualifications
- BProp (UoA)
Industry Experience
Ben has been with Opteon for eight months after completing his Bachelor of Property with the University of Auckland in 2022. He has assisted in the successful completion of roll maintenance deadlines having gained experience in residential, rural and lifestyle valuations.
Areas of Expertise
Throughout Ben’s time with Opteon, he has been building his expertise in residential and lifestyle valuations.

Ewen Lilburn
Formal Qualifications
- New Zealand Certificate in Engineering
- Bachelor of Business Studies (Massey University - ongoing)
Industry Experience
Ewen has over 15 years’ experience in the property valuation industry, primarily with Government services throughout the Northland region. He is proficient in residential, lifestyle and rural valuation techniques required in the maintenance of the District Valuation Roll and has an in depth knowledge of legislation that impacts rating valuation methodology.
Ewen provides specialist expertise in index creation and statistical interpretation of mass appraised data gleaned from the successful implementation of fourteen district revaluation projects. Ewen’s engineering background brings to Opteon added knowledge of data integrity techniques and the ability to streamline workflow processes for accurate outcomes.
Areas of Expertise
- Residential and lifestyle property valuations
- District Revaluations
- Mass valuation modelling
- Territorial Authority account management
- Asset valuation for private and government clients

Mark Grinlinton
Formal Qualifications
- B Com Ag (Valuation & Farm Management), 1984.
- Registered Valuer, 1987.
- Associate status of the New Zealand Institute of Valuers, 1989.
- Senior member of the Property Institute of New Zealand, 2005.
Industry Experience
Mark has been responsible for the delivery of over 30 revaluations since 1999 and held leading valuation positions with Valuation NZ, QV, Landmass and Opteon. He began his valuation career in 1984 in the Gisborne office of Valuation NZ. In 1989 he moved to Tauranga and held the position of Rating Valuation Manager for Quotable Value from 1999 to 2004. From 2004 to 2015 he was a director and shareholder of Landmass Technology, until its purchase by Opteon where he held the positions of General Manager Government Services and Rural Director until early 2019. Following a brief absence, he has returned to add his significant experience and assist Opteon in his role as Registered Property Valuer.
Mark has been a Registered Valuer specialising in the delivery of rating valuations for most of his 36-year career. This experience has led to a strong understanding and long involvement in the Rating Valuation industry.
Areas of Expertise
- Specialist in all aspects of rural valuations.
- Management roles extending two decades in the successful delivery of Rating Valuation Service Provider contracts.
- Strong understanding of the Rating Valuations Act 1988, associated Rules, the Te Ture Whenua Act 1993 and relevant case law.
- Comprehensive knowledge of the Land Information New Zealand audit requirements.
- Expert witness for Councils on many Land valuation Tribunal hearings, including cases of national importance involving Maori land and forestry.
- Member of the expert committee that reviewed the 2008 Rating Valuation Rules.

Martyn Oostveen
Formal Qualifications
- Bachelor of Commerce (Agriculture) Majoring in Rural Valuation and Farm Management from Lincoln University.
- Full Member of Property Institute (MPINZ)
Industry Experience
Martyn is an experienced rating valuer and has been with Opteon for almost 5 years and during this time has participated and managed several revaluations. His experience extends to dairy, pastoral, lifestyle and residential valuations. Martyn prides himself in his knowledge in rating valuation legislation and the quality assurance of valuations and data. Martyn is working towards becoming a registered valuer in late 2020/2021.
Before valuation career, Martyn worked on a dairy farm employed as a manager.
Areas of Expertise
- Rural valuation
- Mass Ad hoc modelling within Valor database
- Mass indexing
- Rating legislation
- Management of valuers and rating staff
- Revaluation and maintenance audits
- General technology
- District valuation roll computer systems

Mate Finlay
Formal Qualifications
• Bachelor of Property (University of Auckland) 2016 - 2019
Industry Experience
Mate graduated from University of Auckland in March 2020, where he completed a Bachelor of Property. On completion of his degree, Mate joined the Auckland Council as a Graduate Valuer where he conducted Rating Valuations across the Auckland property market. Mate joined Opteon in October 2020 where he has since moved his existing experience to conducting Rating Valuations in Hamilton’s property market. Mate has undertaken variations of valuations including building consents, subdivisions, amalgamations of titles and owner objections.
Areas of Expertise
• Preparing valuations for rating purposes (Including in both the Auckland and Hamilton market)

Shelley Manson
Formal Qualification
- Bachelor of Business Studies (Valuation and Property Management)
- Massey University, Manawatu, New Zealand, 1995
- Member of the Property Institute of New Zealand and Friend of the Property Foundation Massey University
Industry Experience
Shelley joined Opteon NZ in early 2021 after returning to New Zealand with her family. She is undertaking residential and rural rating valuations within Western Bay of Plenty, Tauranga City, South Waikato, Rotorua and Taupo District Councils.
Hailing from rural Bay of Plenty and having gained early valuation experience with a provincial firm in Rotorua, Shelley looks to combine her subsequent experience in administration, finance and customer service roles to develop her career and work towards registration.
Areas of Expertise
- Valuations for ratings purposes
- Valuations for Mortgage purposes
- Client relations
- Rural and hospitality sectors

Tom Mabbott
Formal Qualifications
- BProp (UoA)
Industry Experience
Tom has been with Opteon for two-years after completing his Bachelor of Property with the University of Auckland in 2018. He has assisted in the successful completion of revaluations and roll maintenance deadlines having gained experience in residential, rural and lifestyle valuations.
Areas of Expertise
The majority of Tom’s time with Opteon he has been working on residential valuations so his expertise lays here.
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