Help required!

Hi! My wife's Mercedes A-Class has been quite badly scratched in a supermarket car park today! There is a long dent (about 18" long) in the rear door with quite deep scratches through the metallic black paint to the primer coat below.

Can anyone recommend a decent smart repairer or body shop in the Berkshire?Wiltshire/Oxfordshire area? The car is being sold in the autumn so keeping the cost of repair down would be nice...

Thanks guys!