If, like me, you don't have enough time to travel to MRC and leave your car there for days, and you don't really care too much about rolling roads and BHP numbers and just want to keep your engine healthy, I'd recommend these chaps in Hertfordshire. I took my M3 to them for a couple of bits, and there's always a Lamborghini or two in there having work done.
Great service by Gabs and the team. They had my car a day and a half to do the clean, and what a difference it's made. So smooth, and I've now got the 5.5k 'snap' where it feels like it's got a bloody turbo!
Before and after pictures below. Look at the state of it! Previous owners had never bothered I reckon.



Should be good for a mile or two now!