Neil,
Last year I registered an armoured vehicle and the Maidstone office said it would have to be checked by an inspector, despite having a verification letter, photos, etc. This took about 4 days wait, until he was in my area, it only amounts to him physically checking engine and vehicle serials against the application form, then I had to wait until he had reported back to the office and for them to send a letter with the reg number and authorisation to obtain number plates. With the 50:50 chance of having to have it inspected, it would be less trouble to go to a DVLA office nearest to where the vehicle is located. Also, if this is the office that the dealer uses, they may be familiar with the vehicles, so better all round.