Stephen thanks for sharing your costs running the M so far. Although I don't need any more goading to get an M already
However, your calculations are based on doing 6k a year. I do 20k, at which point the servicing costs become more significant, as well as the mpg. Ignoring that for a minute, the £80 additional cost per month for running the //M even just doing 6k a year represents just shy of another £1000 a year. I'd imagine this would comfortably stretch to nearer £1,500 factoring in the extra mileage. I also cannot help but be a little concerned with the resale value of an M with say 90k; even with FBMWSH they don't tend to sell very quickly, or at a particularly good price...
I do see your point in some respects though and as I say, I will have an M in the not too distant future (unless I end up plumbing for a Cayman S... cue uproar at the potentially ruinous costs of engine replacement in those!), but right now I don't think its a viable choice!
I shall therefore continue to enjoy the Si