Thanks guys, I think I'll bite the bullet and make the long drive up to Newark. The car is still in warranty, so they can deal with it. They said it had been checked and serviced! I can't see that with the faults I've fixed so far, and the bigger faults I won't tackle, plus the old air filter etc.
Is there anything I should look out for that might crop up in the future? Is it a good/bad idea to chip tune it?
Thanks, Jay