oh no. Not again...

[2kwik]

Yes guys, I am sure you have been here before! My company car is up for renewal in September and am committed to providing my own so I can have the choice again. Have been very keen on the 330d and 335d - a mate had the latter and was awesome but I have seen the prices appearing for the E46 M3 now (apologies to those selling) and seems a great option.
Despite the obvious scams on mileage and history and 'it has been warmed up properly every time guv', what should I be looking for and would appreciate views on running costs. It won't be quite the 'every day to work' car but won't be far off - round trip of 70miles mostly dualled.
Appreciate any advice given.
Cheers