Potterton 80e problems with reset switch?

LAst night when the heating was switched on, the boiler fired up and all was okay - suddenly there was fuse blowout. I replaced the 13amp fuse on the timer switch mains, but this morning the boiler would not fire up. I pressed the reset switch under the boiler housing, and it fired up while i kept on pressing the reset button. As soon as I released it, it stopped firing.Looks like something wrong with the reset switch electrics or the internal 1amp fuse which I cannot get access to - any ideas / suggestions anyone - short of calling an expert out. THANKS