I've been using Gyeon Bathe+ for a while now, it adds a layer of magic on top of normal shampoo, so it's good for topping up your shine when it's just a maintenance wash. They do a non+ version too without the magic, not tried that yet.
http://www.polishedbliss.co.uk/acatalog/gyeon-q2m-bathe-plus-cat3.html
Got a sample pot of pure in a waxybox and liked it a lot, but it's not cheap even bundled with a couple of other things.
http://www.glacierwax.co.uk/car-care/wash/pure-001-500-ml-car-shampoo-2/
Heard good stuff about this, not used it myself yet though.
http://www.i4detailing.co.uk/shop/britemax-clean-max-ph-balanced-car-shampoo-3.78-litre.html#aBX125_2dG
There's loads and loads of choices out there though