LibDem got squeezed because of tactical voters thinking they'd not be able to win seats and split the progressive vote, that's why Remainers flocked to Labour (in spite of Labour being pro-Brexit). They just hoped Labour would be able to negotiate a less hard Brexit (and avert the catastrophe of no deal). Voting for a party, especially under FPTP does not mean you accept everything that's in the manifesto. The most recent surveys put the Leave/Remain division at roughly 50–50 as it was in 2016. There's no bregret. There's no re-leave.