Clay: Megs clay
Shampoo: makes no difference, I use Tesco's own
Tire dressing: Turtle wax stuff from Halfords
Under Arches: Daisy APC from Tesco, like 70p and lasts yonks, use it for the wheels too.
Then the money you haven't pissed away on stuff that has a high price tag and makes no difference, you can spend on something worthwhile, or if you really want to some wax/sealant.