I'm planning this soon too so would be interested in the same but also what sort of a mess would they make to tongue and groove floorboards as we want to move one of the ones in the lounge too and that's got bare boards that I'd like to keep looking (and fitting) good.
I had this done recently to 2 radiators. We have the original wooden floor boards and, depending on how easy it is to get the first one up, it shouldn't do too much damage. I would guess it will probably cost £100-£200 depending on how much work is involved and what their rate is.
i am a plumber but work for a company, my boss charges £250 per radiator but this includes tha rad. but then again i work for a crook hense the reason im going at it my self in the next few months
Why not have a crack at it yourself. Very straightforward if you have the slightest DIY inclination. Use the £150/£200 the plumber would charge to buy yourself some decent plumbing tools and everyone you do after that is free.