£400 is a bit on the low side for a respray tbh, im sure someone may have had it done at some point but that doesnt mean thats the cost of a respray.
it really depends on the company. insurance/thacham approved places charge the earth. bodyshop i work in recently did a back bumper on a jag couple weeks ago, simple job, left it on, chrome on the top type and we charged £150, now the garage next door is a huge place that has contracts with repairing the local police cars and all insurance work. they quoted him over £900. ive worked at that place too and the work was exactly the same as ours if im honest.
ive worked at quite a few places and tbh, price means nothing at all. if you wanna go spend 4k on a respray then go spend 4k on a respray, but i can guarantee there will be other places that will do it for half that for the same quality of work.
go ask around a few places, get some quotes then ask to see some paintwork fresh out of the booth.
full respray, no major repairs, engine left in, youre looking at anywhere from £800-£4000, dependant on where you go.
you DONT get what you pay for in bodywork, i dunno why people think that. a bodyshop is only as good as its preppers and painters.