The first time I applied I got a letter back saying it had not been possible to identify my motorcycle from their archives or computer systems.
It went on to say that 'Any dating letter/certificate must be sought from the vehicle manufacturer in the first instance'.
Well, I thought that was what I had been trying to do, not sure who they thought had built my 400/4.
At this point I wasn't even 100% sure mine was a UK bike so went down the VJMC route and got a letter from them which was accepted by DVLA.
In the middle of last year, now convinced mine was a UK bike, I decided to try Honda again and this time got a letter from them and a build date of 16 March 1977.
This letter even had a name and a direct dial phone number on it - the first one was presumably from some random jobsworth who was going to remain anonymous.
Woodside - I can give you the details if you think it might help.