Get your heating on and turn all the radiators off - turn on one at a time to see if it warms up then turn it off and check the next one. Thermostatic Rad Valves have a control pin under the control head - sometimes they get stuck down in the off position - take off the head and pull the pin up.. Tweak up the thermostat on the Boiler just a bit to just past mid way - speed up the circulating pump by adjusting the control. If you're content that all the rads can give off heat then go through a balancing exercise to ensure that each one gets its fair share of hot water. If all this fails to work call in an expert but avoid British Gas who will want to power flush your system for £700.
Good luck...
Peccavi
September 2010
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix home heating systems.