The conventional wisdom at the moment seems to be that only 30 or 40 right-wing Labour MPs will go into the Tory lobby tomorrow night to vote in favour of bombing Syria. That's a suspiciously low estimate, and is in the same ball-park as the number that might have defied Corbyn's whip if he had bothered to impose it. So I'll believe it when I see it, but for the sake of argument let's take the upper figure of 40 at face value, and let's also assume that the Lib Dems will vote with the Tories (which inexplicably they seem to be moving towards), and that there will be around 10 Conservative rebels. That leaves us with -
Voting for air strikes :
Liberal Democrats 8
TOTAL : 379
Voting against air strikes or abstaining :
Plaid Cymru 3
Independents (suspended from SNP) 2
TOTAL : 262
I'm making some other guesses there, because the last I heard Douglas Carswell of UKIP and the independent Northern Ireland unionist Sylvia Hermon were both claiming to be genuinely undecided. But given their political orientation I find it hard to believe they won't come down in favour of British military action in the end.
As you can see, there's no realistic way Cameron can lose this vote. The most that can be hoped for is that as few as possible Labour MPs cop out by abstaining. If something close to 262 MPs actually vote against air strikes, that would at least severely undermine the claim that there is any sort of broad consensus. It looks like 57 out of 59 Scottish MPs will be voting against, so it certainly can't be claimed that the UK as a whole is united behind military action.