Potterton Puma 80 - hot water ok, but no C/H, bypass Temperature Sensor?

My Potterton Puma 80 C/H has decided to stop working.

It started up first thing this morning, then after 30 minutes stopped and won't come back again. The hot water is fine, no problem.

After running through the fault finder i've deduced its the C/H Temperate Sensor.

Is there any way i can bypass the temperature sensor as a temporary measure before calling the engineer on monday? I don't think i can bear the weekend living in the cold!!!

Cheers,
Rich