esawers: Methven have a 20 year warranty if you have the original receipt for your old one.
20 years only applies to the tapware which did not fail. Only 10 years for spares, and it is true that the O ring failed within the 10 years, but I failed to recognise it. In hindsight, I should have removed the tap first and identified the issue, and could have just bought a new o ring, new mounting screws and nuts and new mounting plates. In the end I installed it myself, so have a new mixer and only spent an additional 30 dollars on a tool needed to unscrew the tap underneath the basin.