Result, I had something similar with my old Potterton, I found exactly the same site discussing replacing capacitors but didnt want to end up making it worse, so bought a replacement from ebay, swapped it out and it worked fine - cost me 30 quid. I then thought ok lets try changing the capacitors on the old board , which I duly did and put it back in the boiler and it worked 100% too So I now have a spare if required. As it happens it was easy to spot the capacitors were at fault on mine becuase they had actually mushroomed up - not the board in question but this pic shows what to look for , the lines in the top of the capacitor are there to allow the top to dome if a fault develops. This then gave me the confidence to replace the capacitors in my faulty Thomson SKY Box , another result