Any heating engineers/plumbers about?

I've recently had central heating installed and things don't seem quite right. Basically one rad keeps going off for say half hour to an hour and the none of them seem to respond to the TRV's, they're either off or blazing.

I'll have all the TRV's fully open and the room stat upto 30 but this one rad will still go cold after a while.

Also the boiler seems to stop start all the time even when the timer is on constant.

Any help gladly received.
H.