EP 3000 is the timer /programmer not the boiler but no matter...
Heater = Radiator (probably) but no matter...
Cold rad may need bleeding to let excess air out - Should have both valves open. If one valve TRV type then control pin may be stuck down - easy to fix.
Otherwise the available heat may be being used up by the other radiators. If so increase bolier stat a bit if you can, speed up the circulating pump a bit if you can.
If still not better, fully open the cold radiator's outlet valve and partially close the outlet (lock shield) valves on the warm radiators.
Peccavi
January 2009