You need to identify which style of wheel you are thinking of fitting - this site might help:- https://www.alloywheelsdirect.net/bmw_alloy_wheels/1_series_f20_alloys
I looked at a couple of them, and they seem to be staggered with 7.5J ET 45 fronts and 8J ET52 rears so they ought to fit OK.
Standard 18" staggered E85/86 wheels are 8J ET47 fronts and 8.5J ET 50 rears.
But the F20 wheels will sit a bit further into the wheel-arches so you might need to fit spacers as well so they don't look lost!