Boilermate 2000 - desperate for help!

Hi,
I have a Boilermate 2000 (paired with an Ideal boiler) and last year had problems with the central heating not working. A plumber friend diagnosed a faulty pump, which I replaced and it still didn't work, so he said it must also be the PCB. I replaced the PCB with a refurbished one, which fixed the problem - until this week. Now I have exactly the same issue. When turning the heating on it will fire up and the pump starts and the radiators will start to heat up, but then it clicks off and the top green light on the inside of the unit goes off. I've had a couple of plumbers say it is probably the PCB again. The refurbished PCB came with a 12 month warranty, which it is still within. However, I contacted the company I purchased the PCB from and they say that it is extremely unlikely to be simply another fault with the PCB without some other issue being behind it, and if there is another issue they won't cover it under warranty! I've been advised to pay the Gledhill £350 fixed price repair, but of course I do not want to do this if it is simply the PCB, which I ought to be able to get replaced under warranty. The PCB company want me to send the PCB back for them to test before they'll replace it (fair enough), but I've got small kids and having no heating or hot water for several days is less than ideal! Can anyone advise on the issue? I'd be very grateful for any help!

Thanks,

Tom

What temperature is the unit when the heating stops?

Mike