AS above, people seem to be raving about Bilberry Wheel Cleaner at the moment.
I haven't tried it myself, but Andy (clio-coby) seems to get on well with it.
Once the wheels are clean, I would suggest taking them off, claying them, polishing them with Super Resin Polish (SRP) and then sealing them with something, again down to personal choice, like Extra Gloss Protection (EGP). Maybe even a layer of collinites 476 (or another hard wearing wax).