Their apparent policy is to negotiate a better Brexit deal which they'll then put to a referendum where they'll campaign against it.
That's not a policy, its fear. Their party is split between their Northern heartlands who demand Brexit, and their younger southern voters who think Corbyn is cool, who want to remain. We can't do both (leaving with a deal is the only available compromise over leaving without one or remaining in) so they're desperately hoping the "brain dead red" parts of the country will wake up on polling day and follow family tradition. After all, nobody really knows why great grandad voted labour, but its what the family have done ever since.
My home town (Sunderland) is, to be frank, a shithole. It's been a shithole through blue governments, and red. But every election they vote "red or dead" with seemingly no clue that in order for things to change, they have to change who they vote for. Swing seats get investment, 100 year baronies do not. Labour treat my home city with utter contempt and yet still, still the locals can't see past a red rosette. It's all very sad.