My Baxi Solo 3PFL 30/70 is completely dead!?

I have replaced the ceramic fuse (4A) on the PCB and the boiler started up, but made wierd noises. The it went dead. There's power on either side of the replacement fuse and the water pipe temp. sensors are in contact with the pipe. There is no obviouse sign of damage to components on the board.
What can I check before resigning myself to £100+ expense?

Please, is there any 'Corgi' boys out there who can help?

James Skinner
(01908) 630370)
07944 156 717
email: jimskinner@hotmail.co.uk