I couldn’t find a good MB specialist in Bedford (I have spoken with Millenium but not used them - very knowledgeable), so I always use Wayne Gates in Watford. Opposite Millenium you have STS and they can do general work. Bit further afield you have Nick @ Parkham Garage in Wellingborough who knows Mercs and has STAR. You also have Dove House in Rushden who are excellent (but not an MB specialist).