Derry is cheap as chips for everything. There is a valet place on John Street on the way up from the Foyleside roundabout to the top deck of the Craigavon Bridge. Failing that on the Strand road across the way from Sainsbury’s there are a couple of back street garages that are highly reputable. They may do it or if not, will certainly recommend someone at a good quote. Donegal etc seems to be more expensive than Derry as Derry still suffers as an economic black spot.