The law is changing re:servicing - car manufacturers cant hold back service information, technical diagrams etc from regular garages anymore so they will be just as good - just ask if they have the relevant diagnostic kits as obviously they might not buy the stuff for each car manufacturer!
On a Fiesta it wont matter a jot about the Ford stamp when you trade it in, on a BMW or Merc maybe - but even then, if you used a BMW or Merc specialist it wouldnt make a difference.
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Now in a 2009 PB Ford Focus RS!