It has taken a long time for remain voters to suss the Labour party, the old quip of having a monkey as leader would still see them getting support from the heartlands. Corbyn will doubtless come out with some tosh about a referendum on a deal then say he was only talking about an opposition deal and not his own deal, if he ever got into power.
The LibDems and Greens need some kind of electoral alliance and to tell the electorate that if they win a majority in a GE they will revoke article 50, that gets to sixty percent of the electorate and should sweep the board... the level of political honesty of the LibDems will, however, be shown if there is any attempt to throw in nefarious policies such as land tax on the back of their unusual popularity.
No, they should concentrate on PR. doing something useful like building an excess of social housing and radical tax reform that moves some of the burden of taxation from the individual to companies - such as phasing out council tax in favour of a turnover tax on companies, taking the opportunity to also replace business rates and employer NI with a similar tax. That will free up some much needed spending power for individuals and level out the playing field between online and real shops. Turnover taxes are useful as it is much more difficult to obscure than profit.
Staying in the EU with a responsible but caring government should finally rescue the UK's reputation and result in a nice little boom, whilst PR will change British politics once and for all.