I alway found the Auto Glym Body Conditioner or whatever they call it to be fairly decent.
I went on a spending spree when I bought Nicole though in May '10 and decided to try some Sonus High Gloss Shampoo which I've been using ever since. A bottle will last more than a year based on 25-30 washes in that period, it smells nice and it helps the Mitt glide across the bodywork nicely. Roughly a tenner a bottle.
We now have the newly-released 1 litre bottles of Dodo Juice Born to be Mild and Dodo Juice Sour Power in stock. They're much more heavily concentrated than most shampoos, which means they last significantly longer. We also offer 5% discount to forum members.
AutoGlym bodywork conditioner
Dodo Juice Born to Be Mild
Chemical Guys Maxi Suds 2
Chemical Guys Extreme Bubble Wash (special edition for charity)
Chemical Guys Citrus Wash & Gloss
Wolf's Chemicals Nano bathe (I think that's the name as I currently have Wolfs Hardbody on the car)
(I also have others but I rarely use them).
But the one I keep coming back to is Dodo Juice BTBM.