Today the plumber came round to fix the boiler (Yes I know it sounds like the beginning if some cheesy Swedish porn film). After he replaced the thermocouple it still wouldn't light. He suspected the electrics but didn't know how to test it. Along came me with Mr Multimeter. After a few seconds of prodding about in the plug I tripped the mains power, at least the plug was working. I tried to test the second plug but i couldn't get the probes to touch the contacts inside. However after reconnecting the plugs the boiler fired up again. Looks like the contacts in the plugs had oxidised, moving them had remade the contacts. Who needs a plumber when its that simple.
Note: I don't advise making big blue sparks around a gas boiler. Sparks and gas don't get on well for some reason.