"The only way out of this is to form an alliance of at least Labour, LibDem, Green and SNP."

That would condemn me to voting for the LibDems round here. I did that six times in general elections to try to keep out the Tory. Last time I did it, in 2010, the LibDem candidate's repeated (ad nauseam) mantra was "Don't let the Tories in here." Well whaddya know. He got elected, and they ditched their principles and went into an unholy and opportunistic alliance with the Tories, which he supported. Progressive party my arse. It's a cliche, but the LibDems showed themselves to be a bunch of naive Tory-lites, and the one delicious thing about the 2015 election was that they got their just deserts. I don't wish to be disenfranchised via the unholy alliance you're suggesting, thanks. In fact, the first thing I'd do is tear up my membership card.