Go to r-tech have not herd anything bad about them plus look at the price of AmD then look at r-tech check the price and it may be the same after petrol to dtive up there and get a realy nice company treat u good i have had mine done at AmD and all i can say is im a unlucky person who had bad problems but thats not for me to say you wont Just look around before jumping unlike me.
mate i was in the same situation as you, was gunna go amd for convenience. but after speaking to people on here, n calling them both up, i decided rtech was worth the journey. yeh cost a bit n petrol but was worth every penny. brilliant service, brilliant outcome and you'll love your car afterwards and it doesnt break the bank =] they even told me my car had been running in limp mode probably since i got it, (which i didn't no... and 3 garages all failed to identify) n fixed it with his own parts from his car.
i cant comment for amd, but i couldnt recommend anywhere but rtech, shame so far from me or id go get more done, but they may have to wait a few months haha =] but as prev guy said, look around the forum n read reviews, i dont think you can find a single bad post about them. and its truly deserved.