I guess - but I have had this saga recently.... Just like you but with a potterton profile 100e.
The symptoms were reluctance to light the main burner for anyting from 20 mins to 2 hours - the pilot would light then then a long wait for the main burner to start up...
The cause was a feeble pilot flame not producing enough heat to tell the PCB control that the pilot flame was actually alight.
The solution was to clean out the pilot gas injector (it was partially blocked) although the manual says not to do this but to replace the injector.
I tried to adjust the gas flow to the pilot (to get a bigger flame) but that was a futile exercise.
Examine your pilot flame. My replacement injector assembly cost £35 and it sits in the cupboard just in case.
Peccavi
January 2009
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix home heating systems.