If things get bad in the UK the EU wouldn't really want the UK back as such. They may however eventually permit the UK to rejoin. Once the UK has jumped through

If things get bad in the UK the EU wouldn't really want the UK back as such. They may however eventually permit the UK to rejoin. Once the UK has jumped through all of the hoops that new EU applicants have to jump through of course. The EU may even come up with a few new hoops just for the UK, to hold it to a higher standard than a genuine new applicant.