The UK doesn't meet any of the usual acquisition rules, and if it reapplied it would lose all of its opt-outs.

It would also need a new referendum with a Rejoin option - which IMO would be unlikely to happen for at least five years. Ten years is a more realistic minimum - by which time Scotland will have rejoined already, Ireland will either have united or the North will be a bombed-out dystopian wasteland, and Wales won't be doing so well either.

So - not quite the same country, and certainly not an attractive prospect unless it gets its shit together politically and socially.