Could there be a valve thingy switched off somewhere? This happened to me recently ( actually couldn't get heating to work at all) and nice service man came out and clicked the power switch to turn the valves on...cue red face.
I did have a guy out a few weeks ago because my water was not heating up and hence not heating the rads...He just flicked a switch and made me feel like a total dumbo...but obviously he's the dumbo cos he didn't fix that one.
I don't know anything about heating, or plumbing etc
I cannot get the builder on the phone and despite leaving messages he is not coming back to me. My dishwasher is also not working since I moved in and I've been trying to get him about that aswell...its looking like I'll have to pay the manufacturer a nice fee of €136 to come out and have a look.
I'll call in a service man for the rad at this stage aswell I think...