Sounds exactly like an air problem fault. Would try running boiler for 15 minutes turn off and wait 15 minutes, then starting at the lowest radiator working to the highest radiator bleed the air out. You may have to repeat this several times but it is a cheap option to do it yourself as a plumber would probably try this first and charge you for the hours involved. Hope that helps. You could also try turning off all rads except the highest one and see if you can force the air there, but option 1 first.
Stewiesnake, October 2012
