Hi Jambo, it's a bit of an odd one isn't it? Bearing in mind Griff repadded it relatively recently, you would think things are ok in that respect, so misalignment and badly seating pads sounds likely, which I wouldn't have thought was too much for a competent repairer. The feeling I get is that either this horn has taken a bit of a biffing getting to you, or you are the victim of a less than honest seller on ebay.
Is it possible the place in Brackley is trying to get you to pay for more work than the horn really needs? Do they know it's been repadded?
For my money, and bearing in mind you know part of this horn's history, I'd try and get it back to Griff. If you're willing to go to Brackley, travelling a bit is clearly an option. If not Griff, then maybe Stephen Howard wouldn't be too far away.
On the plus side, at least it doesn't sound as if the horn is a lost cause.
Cheers, Bob