As the guys say adapters are the easiest way, but you will need to choose your wheels wisely to get the offset correct else you'll have the wheels proud of the bodywork (not good)
Alternatively, though may not be achievable with a Mini but you could get the hubs re-drilled to a 5 stud pattern. You can usually utilise one of the 4 stud lugs and drill and tape the other 4 to a particular 5 stud PCD. You will need to remove your hubs and only use any experienced machine shop in this type of thing. It will probably need to machine the rotors as well to suite and throw up a bunch of other considerations into the mix as well.