Because we couldn't find the logbook at the time I went through the Approved Vehicle Club route (I saw the very helpful Mr Harmer at North Walsham's Motor Cycle Museum) Had old tax discs and and the last mileage exemption doc they had sent, Club approval form duly issued.
Just before going down to the DVLA (last August) I had to SORN a car I'm using as an organ donor, used the online registration search to check it had worked and just out of idle curiosity typed in the tractor reg, an entry came up (with not much info) to my surprise.
Next day at the DVLA the lady couldn't have been more helpfull, looked at the various bits of information then picked up the screen print of the DVLA page 'whats this?' came the question, when I told her she went off to a computer terminal and came back with a different form, The 'Club stuff no longer needed) yes while not taxed it had got onto the computer somehow, so that was just a change of registration

Try as she could she could not overcome the fact that having been registered to Dad, he was most inconsiderately unable to sign it over (having gone to plough elsewhere) so I had to go in the following day with a copy death cert. Also did my Series 1 80" Landy at the same time again with no Club stuff needed as also on the computer.
A couple of weeks later the V5's came back, I trotted down to the PO for me tax disk, nope Swansea had done something, it came up as a disabled vehicle (I pointed out it had no battery, tank or front wheel and I've got a bad back but that didn't seem to help) Phoned Swansea and after 2 complete drongo's spoke to someone not on a help desk, 'They must have filled it in wrong in Norwich' was his comment, take it back there or send it here for amendment.
Third visit to Norwich and 'my' victim was not there, the chap I saw was equally helpfull, took exception at the Swansea take on things and went and got the original form, you've guessed it, nothing about disabled vehicles ticked, just vintage ones
My experience is if its already on the database and you are not in a hurry you should be OK approaching them yourself, not needing the 'Club' stuff, I think the club 'scruntineers' may well be needed to mediate on stuff which ought to be rubber stamped within the DVLA simply because they may have found a sensible contact. Otherwise follow Brians recipe as the safest route and any vital docs - don't trust to unregistered post !
Happy hunting and remember that we live in a universe where matter and energy are finite, sadly ignorance and indifference in some government departments may be infinite
Oh and if a reg is on the database expect the DVLAKGB to send you a nasty threatning letter about trying to deceive & mislead them by not SORN ing it - nothing further heard on either of my vehicles, if they wanted a SORN all they had to do was ask
I see annual SORN and paper tax disks look like they are on the way out..........