I would have though for around £400 you would receive an excellent respray and not see any difference from the OEM spec. Worth looking at some of the specialist restorers and not just accident repair facilities.
If you want a top job, including removal of the bumper plus some (superficial) repairs, you certainly wont get change from £400. You might get someone to give it a sand down, fill, prime and paint, on the car, masked up for £150ish upwards.