The regulations regarding energy efficiency state that room thermostats should be fitted, but I always instruct people to turn the room stat up full and forget about it and use the thermostats on the boiler to control the temperature of water and heating. So whats the point in room thermostats if you're not going to use it.
Myself and many heating engineers that I know, do this because:
a) alot of elderly people find it alot to take in that when changing from a gravity sytem for example over to a combi boiler because there's a room thermostat, a thermostat for the central heating and a thermostat for the hot water.
b) the room thermostat only controls the temperature of the room its in. For example if the room thermostat is set to 20 degrees and this cuts the boiler off, at the other end of the house it could be alot cooler.
So the position of a room thermostat has to be given some consideration, no good opposite a window or above a radiator etc
Hope I'm not too late in answering this, I would kill two birds with one stone and use a programable room thermostat, this give the best efficency as you can control both time and temperature with one unit. When choosing your boiler look out for the ones with the extended warranties as standard as they are made from stainless steel and will last much longer than there one year warrenty cast aluminiumn counter parts. The stainless steel boilers also will be A energy rated which is good news for the gas bill