Thanks guys, still buzzing from the M day. Never dreamed i'd be drifting the new M4 on a skidpad before the car was even released... amazing.
SOLD the E60 M5 today, pending AA inspection happening tomorrow. Lost a bit of money on the car which is a bit upsetting, but because the W211 E63 is such a relaxing easy-going car, the loss isn't so bad.
I can see myself going back to BMW one day though.