BUT... if May's deal fails and parliamentary rules mean that it can't easily brought back for a second go, then that course would pretty much ensure a no-deal Brexit - because all the other routes May might take have been tried and failed (renegotiation) or would be unthinkable to her (calling a second referendum). It would only need a few Tory remainers to put their remain loyalties above their Tory loyalties to tip the balance. Some of them have safe seats, too, or (like Ken Clarke) are likely to retire, so have nothing to lose in terms of a future election.
So, I'm not so sure that a vote of no confidence would be won by the Government after all. (Though it probably would be. No one ever lost money by overestimating the Tory instinct to cling on to power.)
Anyway, we'll see soon enough.