MmmBeer
Brewer
The best and most reliable A/G kits I've tried came from homebrewonline.co.uk they sell Brewolution kits. Bit dearer than some (£21.95/23litre) but worth that little extra IMO. Never had anything but excellent results using them.
Also Beerhawk.co.uk do a few good ones. Their Irish Red Ale is good.
I had a few Northern Brewer kits from Beerhawk and they were all excellent. They are expensive, but if you find one you like, it's easy to find a recipe to make from scratch for half the price.