boiler not firing up

Hi,
Came back after weekend away and boiler on Boilermate 2000 system not working. Have checked gas supply and electrical supply and no probs. Plumber has been out and says to change control unit, which I understand is notoriously unreliable but also one of the most expensive parts to replace.
Is there anything else that I can check before forking out £300 on a new control unit? I have seen them advertised on tinterweb on what look like bonafida sites. Wondered what you thought? Thanks,
britprac.

It looks like the ACB.
But best to carry out a few checks as well.
Look through the BM 2000 posts.
Lots of info.
Mike