You have NOT made an expensive mistake! The struts will fit on but I think your car may have the electronic dampers, in which case goos luck with disconnecting them.I have done the same thing, thinking the M5 legs wouls be higher spec but they are`nt, lesson expensive. There are two diameters of sensor, early and late, you have late,struts bolt to legs so should not be a problem.Shocks will give up fairly soon, buy Boge/sachs replacements, lesson learnt!