these companies are very good - I used 'Revive' a national franchised operation on my 4 year old E class for some abrasion scratches on bumpers and a small dent. I was pleased with the work - it is acceptable and almost invisible, but for the price much cheaper than a body shop.
One tip - when getting a idea of cost over the phone, don't say it's a mercedes, say 'my car' or something - I saved £20.