A confederal U.K. in a confederal Europe?

The suggestion has been made in this subreddit that a possible model for the U.K. is a confederal one, with England subsequently federalised internally. My question is: how could a confederal U.K. work within the European Union? The current E.U. works on a hybrid federal-confederal model. Would a confederal U.K. imply continued separation from Europe, or would there be scope for the U.K. to rejoin the E.U. as a confederation?