Maybe a quick run down the M1 to Monkfish in Milton Keynes? I think Pentagon Vx in Derby are authorised for service if you want to go the dealer route...
Pentagon vauxhall are useful agreed as there one of the approved vxr8 dealers....I've been there a couple of times with helpful guys there. Other than that use walkies or monkfish if you fancy a drive out.
Another thumbs up for Pentagon Burton on Trent, so long as it's routine servicing or a common fault. Anything more in-depth and I'd definitely take it to Monkfish or Walkinshaw.