Wonder Wheels, the alloy wheel cleaner, is made by the famous company Carplan. Wonder Wheels product is now available in a trigger bottle. The company is well known in the car industry, and Wonder Wheels have their own section on the Carplan website :- http://www.carplan.co.uk/index.cfm?category=0
The contents of the cardboard box are, 500ml of wheel cleaner, one application bristle brush, and a dispensing container. This size costs around £7.50, which is a pretty average price. This may sound expensive, but a little really does go a long way.
According to the instructions, you should use straight after washing your car, that way a lot of the dirt will already have been cleaned off, The cleaner is painted onto the wheel with a brush provided, this should then foam. Leave this to soak for a few minutes, and rinse with clean water. That is all there is to it, your alloy wheels should now be immaculately clean. Personally I recommend that you wipe them dry with a leather, and apply polish, this will help to prevent dirt, tar, and brake dust from sticking to the surface.
Your front wheels will accumulate a lot of dirt, because front brakes do most of the stopping. The black grime you are removing is brake dust. Years ago this was mainly asbestos, which although a very good friction material, was not good for the health of anyone breathing in the dust. Nowadays brake pad materials are not as effective, but better health-wise, and they do tend to wear quicker, hence the black dust. This dust is not harmful, although it does look rather ugly, unfortunately most alloy wheels tend to be silver, and therefore show up black dust.
You will be able to source this product at many places, such as Halfords, A1 Motor Stores, plus all the larger DIY supermarkets, and all good motor accessory shops. My alloy wheels are sixteen inch, with thick spokes, so they are easy to keep clean. Wonder Wheels is probably most effective on the small multi-spoke wheels, which are becoming more popular nowadays.
As you are cleaning your wheels, please have a look at the tyres, check the amount of tread, are they wearing evenly? What are the pressures? Can you see any cuts, bulges, or any foreign bodies stuck in the tyres? If possible, try to keep stones etc. out of the tread too.
I can personally recommend Wonder Wheels, just remember it is produced for alloy wheels which have been painted then lacquered, (some alloys are just burnished alloy) in this case, do not use. Also remember that this product is acid based, and will eat into unprotected alloy wheels. I would recommend touching up faulty paintwork on your alloys, especially at this time of year.