Thanks for that mr wilks, it's really helpful to get experience from a former owner of more than one of each! :thumbup:
So it looks like the M may have been in Tax Band M because BMW hadn't quite got the hang of getting more favourable CO2 ratings in the mid 2000s, but by 2010 they had. :lol:
My M has Sat Nav so I could look at mpg for Journey 1 and Journey 2, etc. but I don't really want to know!