check it out at bmw warranty website, i was looking at 7 series recently then noticed the £1800 a year warranty price (with £100 excess and no breakdown), i'd take a wild stab and say the 6 wont be much different?
Looks to be around £1300 if mileage is under 100,000. I guess it boils down to how reliable they are, I'd imagine a gearbox or ecu failure would make it worth while. Having said that, I'll probable keep the car for at least 3 years so is it likely to cost much more than £4k in non-routine maintenance? Who knows. It also depends how decent the actual warranty is, I'll look at that now.
It appears that the facelift models have the N53 engine which is less reliable than the N52. Obviously the pre-facelift is cheaper to purchase as well so I will try to sit in them both, from photographs the facelift interior, unsurprisingly, looks a bit nicer.