IMO there’s some bad blood between the UK and the EU.

Not so much that it matters. The financial industry wants them back in the fold. It would be a win-win for UK and EU. But there is one or two maybe major cons for the UK: They won’t get the UK rebate back and they won’t get any other exceptions. That means they’ll have to switch to the Euro.
They’ll probably accept paying the same as the other member states but I’m not sure if they’ll accept the Euro.