Thanks to this and other forums I have sorted out my potterton problem by resoldering my PCB. The board was a disgrace and looked like it was soldered by an eighty year old hanging upside down, the quality of build resulted in the failure. I messed around for quite awhile with the overheat thermostat and bridged it out to eliminate it from the enquiry. The PCB board was replaced last week and as of today no lockout whereas previously it was becomming more and m ore frequent. A 10X magnifying glass and a light source can easily identify the cracks in the solder.
