Cleaning car alloy wheels

Cillit Bang, but wash it off quickly and thoroughly. You can buy expensive compounds such as "Wonder Wheels" to do the job, but chemically it's very similar to Cillit Bang, a mixture of sulphamic acid, a detergent and a lot of water. And acid cleaner is needed to get the baked-on brake dust off the wheels. Once you have them clean, don't use it again, regularly clean the wheels to keep them in good condition.

Over use of an acid cleaner will damage alloys.

Wonder Wheels.

I polish mine with car polish as most of them are actually painted rather than just polished alloy and it seems to stop them getting dirty in the first place

Polish certainly can help once they are clean. The problem seems to be hot dust from the brake pads eats into the paint - some cars being worse than others.