Re: Walls have been plastered/ is damp now drying
i take it seein as u got a back boiler u also got a hot water cylinder? means the system is a gravity system, the boiler heats the water in the cylinder..
a combi heats water directly on demand, bit like an electric shower, but gas powered with more flow rate..
to change from a gravity to a combi you need to feed gas to the combi, no problem...connect the combi to the flow and return pipes of your central heating...again, no problem lookin at the pipework, i expect youve old style floorboards upstairs...
you also need to connect a mains cold supply to the boiler, and connect it to the hot water supply to the house...
site the boiler in the airing cupboard upstairs, send the flue through the roof (or through the wall should it be adjacent to an external wall)
couple of system flushes and all should be well..
find a heating engineer to do the job, let him take away any copper removed (cylinder etc)...make good yourself...should be all in for 1000 possibly less...
that said, i aint a heating engineer, i speak just from experience doin houses up etc...and were on the plastering site...food for thought though if your stuck for ideas...