If any of you UK people are interested, I just booked my M5 in at my Local BMW dealers ( Bowkers in Preston Lancashire) for an oil change and valve clearance adjustment. There prices are as follows:
oil change using semi synthetic oil(cant remember the brand but i doubt it will be a poor quality one) and new oil filter and plug washer, 80 pounds all in.
Valve clearance adjustment on all 24 valves, 140 pounds + VAT minus 10% discount. Thats for labour, theres a rocker cover gasket to add to that at 23.08 + VAT minus 10%. i was told that the rocker cover gasket on the M5 was re-usuable 3-4 times. The dealer wouldn't have that and has insisted on a new gasket, which i'm not complaining as as i'd rather have new!! stops all those pending nasty oil leaks.
Regards
Mike K