Mintex have started claiming their brakes are dust free. While this seems unlikely,
the material has to go somewhere, their red box pads have a good reputation for
low dust. I have no experience of these pads. I couldn't find the Mintex claim so I
don't know the name of these pads are supposed to be dust free so you'll need to
call Mintex to find out if interested. Freely available for the MINI is EBC greenstuff
which are good pads I have used in the past and can testify to their low dust formula.
In the states there are brands like PBR/Repco/Axxis Deluxe that have similar
reputations. Try searching long running forums for experience of these pads.
Keeping wheels clean is not a MINI problem though white wheels does seem to be
asking for trouble