Hi Faster
Try these guys
http://www.turbochip.co.uk/Car.aspx
They did my RRS 3.6 TDV8, they are based in Carlisle but have agents all over the UK and will come to you.
My RRS had a massive improvement, knocked in an extra 50bhp, and will remap for free if the BMW guys reset it when servicing.
Nick is the guy you need to talk to.
Also try David at
http://www.larinisystems.com/ for a really high quality exhaust, again got one for my RRS.
kadeSdad