Technically as has been said you must declare it, wether you do is up to you, and no one is going to tell you to break the law. The Apple guarantee is world wide, so your covered there. If you buy in an Apple shop they will set it up for you with an existing apple id, if you have one. Haven't checked recently but are you saving any money, a few years back when you were getting $2 to the pound it was worth it, but nowadays not sure.