Yeah, this is why we need a decent preferential voting system, so then you could rank your preferences 1) Lib Dem, 2) Green, 3) Labour or whatever (that'd be my preference), and not have to worry.

In this case, I think Slaughter is safe. He had a substantial majority at the last election, the worst for Labour in many decades, and both the Tories and (especially) the Lib Dems are now much less popular. That looks like a very safe Labour seat to me...