There are two ways your DB can get a Costco card. Add him as your spouse on your USA card (I'm still using my USA card), or if he qualifies for a UK Costco card (Civil Servant, works at University, etc...) The listing is on Costco.co.uk, which also lists the warehouse locations.
and, as was mentioned, freezers are smaller, so although it's great to buy in bulk, I've found that I really have to think about what will fit before going crazy. Best buy.... AMERICAN HOT DOGS, the costco kind! UK hotdogs have no flavor! Also good is the kitty litter.