Or Goodbye both and Hello post-Empire Economic Commonwealth? Continental entanglements have been nothing but messy, there is an argument for focusing on the Empire and avoiding unnecessary alliances that just bring trouble. Of course that does assume there is no 'hanging onto Empire at all costs' mentality, but frankly I can't see Halifax doing that. He may not be keen on it but I can't see him fighting too hard (and certainly not militarily) if the colonies really want to leave.And if the US invasion fails, things get really bad - expect acqusations of being left in the lurch etc (a bit like British reactions to the US after Suez, only 100 times worse).
Hmmm ... I think its goodbye Special Relationship, Hello Europe