Assuming Boris manages to get all the conservatives and all the dup (he may well not)
I think he could rely on a number of the now ex conservatives who voted for Mays deal in the past... Clarke Hammond gauke... I'm guessing he wouldn't need too many other votes
As I say I think it will have a referendum amandment tagged on to it and pass with the amendment
Thinking about it, why would they pass it with a referendum amendment if they despise the deal so much?
They hate it and think it's bad for Britain, but will vote it through with a stipulation that the UK gets to vote on it with an option of remain. So based on that, with a lot of people not bothering to do their research on what the deal actually includes, they're happy to let the public decide? What if the public vote for the deal? The MP's obviously don't like it and don't want to pass it, so if a referendum states take the deal they're just going to do so?
My betting is they'd back everything on remain to win, and if it doesn't, they have no choice but to accept this deal, which they don't like. That is why Corbyn doesn't want to add a stipulation of a referendum before an election. He wants the chance to negotiate his own deal then put it to the public. He doesn't want the public to vote on a "damaging Tory Brexit", which is why, in my opinion, he'd whip against supporting a referendum on a Tory deal and flat out rejecting it and going for an extension/GE. Any pre-election referendum would be another straight Leave/Remain if Labour have their way i'd imagine.
Lib Dems won't want a referendum either, as they want to revoke A50 and if a referendum says take the deal, they'd have to oblige, which i'm pretty damn certain they won't want too