My MGB, bought by me in May 2000, was first registered on 2 May 1979, so til recently I hadn't expected to be able to register it as a Vehicle Of Historic Interest til 1 April 2020. Then I discovered that VHI registration is based on build-date rather than registration date, and dithered for a while whether it would be clever investing £47 (£43 + postage) in a Heritage Certificate, that might only confirm 1979 was the build-date, too.
Then I noticed the small-print on the British Motor Industry Heritage Trust website says there's a web research service that allows you to ask one e-mailed question - such as build-date - for a flat £6 fee. The answer, which came within two days, isn't accepted by DVLA as evidence of build-date. But it's a solid way to find out whether you should spend that extra £47 for the Certificate, which is accepted as proof. My '1979' MGB turns out to have been built on 3 October 1978.
https://www.britishmotormuseum.co.uk/ar ... n-services
There was a fuel crisis around late 1978 that slowed car sales. Lots of cars first registered well into 1979, like mine, were probably built in 1978, and you could save yourself an extra year's tax and - if you choose to not have one - the MOT costs too.
If you're around central London, you're also excused the new Ultra Low Emissions Zone Charge.
Allan T