I'm guessing a 110k 318 with fsh would be okay as its been looked after? I just assumed valves etc etc get worn etc at higher mileage? I guess I'm just scared of going with a car with high mileage as my car is low?
Generally, yes, 110k should be fine.
As an example, I bought my first 318i (e36) @ 125k and sold it @175k all it needed in that time was a back box and servicing, it never even had a clutch replacement!
It had some valve work done @90k, long before I bought it.
I know of an S plate 318i e46 with 310k on the clock and bar a lot of stone chips on the bonnet, it looks and drives fine.
The guy who owns it paid £350 for it, trick was buying it from its first owner who'd clicked the miles up using it as a company car, retired and kept it , and always took it to BMW for servicing!!
Such gems are rare, but out there.
Buy on condition, not age nor miles IMO.