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Here is the (two dimensional) political placing of the parties in the forthcoming UK election from Political Compass....
If you thought you didn't have an awful lot of choice, the fact that all major English parties are (on this assessment) siting in the blue (Right/Authoritarian) quadrant will confirm that suspicion
Edit: SNP offer an alternative in Scotland, of course! (apologies for missing this earlier)
@ChrisMayLA6 @melanie @PoliceStateUK sadly the only way to unseat the Tories is vote Labour, as protest votes will not have the desired outcome. Labour have sold their principles in pursuit of campaign funds. Vote for them, but protest and hold them accountable
@Offbeatmammal Not Labour everywhere. In some seats we need Labour fans to vote Lib Dem, often uni towns iirc.
https://tactical.vote and a few similar sites have the best advice for each seat.
@PoliceStateUK that's actually really good to know (expat voter, sadly where I get to vote us staunchly blue). Hopefully L and LD can play nice together and be strategic
@Offbeatmammal A few staunchly blue seats have flipped in the last year, so here's hoping 
@PoliceStateUK Beaconsfield might swing independent but unlikely given the mood last time I was back there