That's £200 / £250 quids mate!
Before you buy seek out an exchange service - some operate in the Uk for about a third of the cost of new but you must send the defective one back first.
If you do decide to buy a new pcb have a go at repairing the existing board first - check out this repair story to a different boiler's pcb...
http://kaijaks.co.uk/blog/nick/2008/02/10/dodgy-old-boiler
It's summer for you just now so you've got several months to make a decision.
Usually boiler pcbs are not complicated and cost perhaps £5 - £10 to make - somebody is on the make I think. Good grief - you can buy a brand new computer for a few dollars more!
The weak areas of boiler pcbs are poor soldering during manufacture and electrolytic capacitors failing in the heat - they are sensitive to heat..
Good luck...
Peccavi, November 2009
