I can't help you much with your problem, but I will suggest you get your check engine light codes read so you have a better idea what's wrong. I don't know about in the UK, but some parts store chains in the US read the codes for you free so it may be something worth checking out before you start tearing things apart on your car.
Hatch Nation #13 : Rally Revolution #13 : ROTM Jan '13
It's Bryan, not Brian
RSVT-170 Build in Progress
Derusting Rusty Build in Progress