It's not Birmingham, but just a short journey north (near Nottingham) is Mick at Diamond Motors. If you're after a well-established and reputable specialist then look no further. :smile:
He's looking after my Trophy at the moment.
I had a similar problem a few years back and it was spark plugs. Make sure you get the correct ones otherwise you may still have issues!
NGK PFR6E-10 (3688) are the items to look for, e.g. http://www.roadtrackraceparts.com/ngk-spark-plugs-renaultsport-clio-172-182.html