Boiler continually cutting out?

Hello everyone.

I need some advice please regards my gas central heating/hot water problem.

I have a Potterton 50e boiler which appears to be powering up fine but then cutting out after about 10 minutes or so.

As I said above the boiler itself powers up no problem but after aprox 10 minutes or so the heating part of the gas goes off leaving just the small pilot light on.

If I turn the bolier off and leave it for about 20 minutes and then turn it on again it will power up for a few minutes before again cutting out.

After cutting out it makes all the noises it would make if it had powered up i.e. it doesnt go quiet as if it was off. I have to look through the little window to see that the heating gas has gone off.

If I dont turn the boiler off it remains on pilot continuously and will not then power up properly until I turn it off for 5 minutes.

The rads get warm and we only get luke warm water via the taps.

If anyone can give me a clue to what might have happened I would appreciate your advice.

Thanks in advance.