Decorating behind radiator

A plumber would call, take the rad off, return and refit, fill etc and charge accordingly. Its a case of weighing up the cost involved. Its a possible comprimise to strip the paper off as far behind the radiator as you can ( not leaving any paper loose or stuck between rad and wall) . A tricky and time consuming job but do-able. Then if youre re-papering the wall paper down as far as you can behind the rad (dont go any lower than you can reach) a mini roller(rad roller)with a sponge sleeve can be used to smooth and flatten the paper to the wall behind the rad. Done neatly this can look fine

Always remove radiators and paper behind. Most decorators can remove a radiator and replace and bleed.

I always remove the radiators before decorating the room and put it back at the end and test it before leaving