Thanks Dwayne, actually I am only looking at cruises to Alaska along with other choices, so I haven't actually chosen a cruise line yet. I just want to be clear in my head about what the procedures for uk citizens are.At least I have a bit more of an idea now that Kraftsinc has told me USA immigration & customs are at the cruise terminal in Vancouver.
But I'm still wondering who gets to remove the green visa waiver receipt they attach to your passport.
Because if it does not get back to USA immigration then re-entry to the USA at a later date may be awkward as you have to prove when you left the country.
Hope I'm not confusing you too much.