In Glasgow I have found the Tesco stocks Ritz Crackers, sadly piddly little boxes that do not last me the drive home (all of 4 miles), I really need the American mega sized box of them that will last me maybe 8 miles before I eat them all
If you are in Edinburgh or Glasgow always poke into Pekhams (
http://www.peckhams.co.uk/). They have Hershey bars, Oreo's, Coke (in American bottles), Microwave Popcorn, Skippy Peanut Butter (YAY!), sometimes Arizona Tea, and they can source much else you only need to ask them!
For Costco, does anyone know how membership works over here? Someone told me they only giv you membership as a business or public servant?