Unfortunately TS departments are a bit of a target for costcutting councils and some, like Barking and Dagenham, do not even have a weights and measures qualified officer (which is illegal for the Council not to have) – basically there is about 1 officer for every 1000 businesses or 1 for every 14,000 of the population (about half that level in London)

Departments do have to report to BIS and the OFT and you could try contacting them.

Also two years ago this would have been under the Trade Descriptions Act S14, where you had to prove ‘mens rea’ to the criminal standard of evidence ( the garage could claim mistake or accident and that the had exercised due diligence), the newer legislation is much more flexible.

If it is an unroadworthiness claim then these are difficult anyway, the police won’t touch them more than about 48 hours after purchase.
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TS are not reviewable save by Judicial Review. The JR (which is a High Court remedy) will consider whether the actions taken were within the bounds of their wide discretion, or not. It’s not a simple process and you’d need legal representation.

A slower and more usekess alternative is the Local Govt Ombudsman

Surely your easiest route would be via the Small claims procedure (against the garage) in your local court?
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