Interesting point on the exhaust, I could defintely here a few weird noises from it over the last two months and then it stopped a couple of weeks back. I might take it to an exhaust shop and get them to chuck it on the hoist.
I've got a Walbro 500HP fuel pump which has a 12V connection, so unless thats having problems I don't imagine it will be that.
Cheers again for all your help and ideas,
Tommo.