If, as is entirely possible, the Euro is worth more than the pound at that point you may find that reluctance goes away.
Yes but the thing about keeping your own currency is it allows you keep your own fiscal control and I don't see the UK giving that up, in fact I think a single monitory policy for a whole load of different economies is an issue with the Euro, which of course then gives the argument towards closer integration, but in long term I think that's difficult for a whole bunch of countries that have different cultures, identities and languages etc, plus a whole issue of the EU being dominated by Germany and France.
In my view the closet the UK could ever consider be to the European Union in future would be a Norway type deal and become part of the single market, which would solve the third country issues and some of the paperwork and it wouldn't stop us doing trade deals with other countries, obviously the compromise that some Brexiteers wouldn't like be Freedom of Movement and closer alignment, but on the other hand it is what the likes of Farage campaigned on at the referendum even though he denies that now.
I certainly don't see Labour proposing to re-join, The Lib Dems yes, but despite being a Lib Dem supporter years ago I regard this party as one that lost the plot with no credibility since Joe Swinton's proposal to just cancel Brexit, and haven't regained it since.
Unfortunately it quite difficult to have a sensible debate about Brexit in this country because there are too many nut job Remainers and Leavers and it is a pity we didn't have a much better quality of debate on both sides at the time of the referendum.