Livre d'Or

I'm a Lib Dem, so that should be taken into account here, but the Remainer-tactical voting sites do all seem to be saying that in *all* the English regions one should vote Lib Dem, given current polling (in Scotland and Wales they say to vote for the Nationalist parties in both cases). https://www.remainunited.org/your-voice-your-vote/ is the one that Gina Miller set up, while https://www.remaineu.org is another one.
(For full disclosure, https://www.remainvoter.com/ advises Green instead.)
All three of those tactical voter sites say they will update as it gets closer to the day, so if I were you, I'd bookmark them, check back the day before, and see if it's changed, but if it hasn't Lib Dem is your best bet.