If you don't want zaNu-Labour to have another term, you have to bear in mind the screwed up electoral system in the UK. FPTP means you need to vote tactically in order to keep someone out, as it's a postcode lottery whether your vote means anything or not.
Look which constituency you are in, and see who came where. If Labour won last time, vote for whoever came second last time, they didn't win, vote for someone sensible who could win.