Just a little update on this. I had another go at getting it moving myself yesterday morning to no avail, so decided to use the recovery I get with the warranty. However, the subcontractor who got the job took one look at my drive on Google and said they couldn't do it. As I was parked front in, the couldn't pull the car off and their lifting vehicle wouldn't have room to work and/or would wreck my drive. The main recovery firm (Autogard) then called me to say that as the car wasn't accessible it fell in an exclusion to the policy and they couldn't help. I pointed out that being parked front in on a driveway is hardly an unusual position to leave a car and what was I actually paying for but they couldn't have been less interested.
Fortunately the dealer (DG) stepped in and after much effort on his part I spoke with someone else at Autogard who agreed to try some of their other subcontractors. One was found with a new piece of equipment that they thought could do it but I would have to wait until this morning. The guys from Hough Green Garage turned up with a little remote controlled contraption on tracks that looked like it should be defusing bombs. The gravel seemed to be a problem but they spent some time raking it out from under the car. I'm not sure what the machine was meant to do, possibly roll some plates under the rear wheels, but it gave the rears a good shove which unstuck the front brakes and, ultimately, the car was able to reverse off the drive under its own steam. The pads seemed not to have left any residue on the discs and a short test drive suggested all was well.
As a footnote, I had a pleasant chat with Marios at Autoshield this afternoon who suggested that it is not usual for the pads to stick so solidly to the discs after such a short period of time and thought that possibly the discs had been skimmed at some point in the past. His advice (and that of a number of others) seems to be use it more, however, it was never meant to be a short distance commuter car. One thing is for certain - I'll be parking it on the tarmac section of the drive in future!
Thanks to all that shared their thoughts.