Jeyes cleaner is cheapest perhaps. An old fashioned recipe of Carbolic Acid from DIY shops, wholesalers, etc seems to shift dirt and grease off anything. Wouldn't use it often, but great for getting off stuck on muck from your alloys. Also good for getting oil splashes off the drive, etc.
Wonder Wheels is top stuff though, but it also slowly degrades your alloys if uses too often.
http://www.jeyes.co.uk/Also find tar remover seems to help in lots of situations.