-
It's so hard to say.
I hesitate to reference my own car, but it's just needed servicing from ~35k to ~50k. It has DSG so I spent a bit more on a major service to make sure the oil was changed but nothing else. In my MINI that my folks now have the clutch (iirc) went. From BMW that was ~£2.5k. I'm sure you could get that cheaper from an indy. It's also had a new battery which again was reassuringly expensive from BMW.
With the wealth of info online now, you can usually find out about thinks like the Mini clutch, or timing chains, etc. I feel like most of these big bills are around £2k and you should expect 1 or 2.
Goes without saying that cars like Mercs or BWMs are going to cost a lot to repair just from a parts pov.
to @hoops @TRA 's points, if you buy a modern car with say 40k miles on it, what should you plan and budget to replace over the next 40k miles and what are we talking about in £?