First thing you would be looking at is an outfit that has a spray booth large enough so I would look for coach or HGV people in your locality and ask for recommendations doubt there will be many but by asking them you will get the recommendations and the 'what ever you do avoid them. - I doubt there are 10 in the whole of the west county so don't expect to be over whelmed with them.
New set of factory decals circa £1500 to 2k
half tidy full paint £5k-£7k two/three/colours and clear coat
Can you get cheaper yes
Would you want cheaper depends on age of RV and expectations old Rv two pack single colour £3k-£4k