I have a chemical company near me that makes alot of the car cleaning products that the pro's use before they are bottled into their expensive bottles and marked up to fuck. It is, without any shadow of doubt, the most amazing car shampoo I've ever used and its really not expensive. 5 litres is about £20. I've had a 1 litre bottle they gave me last time I was there on the go since late last year and its still half full.

I get a really good wheel cleaner from them too, its so cheap you wouldn't believe it.