Just come across your post. Try the Kithead Trust. They have the majority of all vehicle details prior to computerisation. It'll cost you £7.50 to find out. If they can tell immediately that they don't have it, then your cheque is returned. However, if they think they have it and do a search, then they keep it. If it is in their records they send you a photocopy of what they have, which is usually on a postcard, which gives when it was last taxed, the last owner, when first registered, the engine size (which may be quoted as hp) and any relevant chassis/engine numbers.
Send a cheque with your request, and enclose an SAE for their reply. They are manned by volunteers so allow time for their reply. It is registered as a Charity.
Kithead Trust,
De Salis Drive,
Hampton Lovett,
Droitwich Spa,
Worcs.
WR9 0QE