Lee

Further to uug197h. I agree that on some occaisions its cheaper to get someone in. (The plasterer has just gone , got done in 3 days what I have been putting off for a year Mrs lee is now walking around with that smug told you so look)

Its always hard to give advice blind,

From your description there are some other things to consider,
Heat control . Thermostat or just TRVs, with a stat we are now talking possible zone control and lots of more bits.
Will the boiler take another rad and still remain efficient.

I would go for the quote option and let a plumber do all the research for you. Once you got that then you look at all the options.

Good luck