Potterton Performa 28i?

Hi, have got the above combi boiler. Last night the electric kept tripping and we discovered that it was doing this when the boiler was trying to heat up. An electrician came out today to check the electrics side, actually managed to get the boiler to fire up before it did again trip the electric but there was a loud clanking noise. Plumber can't come until tomorrow (he is going to do a joint visit with the electrician). Electrician thinks possibly there is block in the flue? What do you think? We have had a particularly icy spell, but it was a bit warmer yesterday than it has been. Yours, cold and wanting a bath!