There was an interview with him the other day on LBC in which they asked if he wasn’t worried he might have his vote split with the MRLP - Monster Raving Looney Party - but he pointed out quite adroitly that they are just as likely to split reform’s vote, so the more the merrier.
It's the 10% chance they are worried about. Reform is very much the Farage party, and him losing to a bin in their heartland would be catastrophic; he would go from being the presumptive next Prime Minister to a national joke.
Binface, ridiculous though it may seem, is going to be the unity candidate for tactical voting, and that's deadly serious from the point of view of those who wish to get Farage out.
Even if Farage wins, but with a reduced majority, in an election where the alternatives are fringe or novelty candidates, it will be hard for his dignity to recover.
He'll likely win alright, but at the last GE, he only received 21,225 out of 45,648 votes cast, (so got 47% of the votes on 58% turnout).
I think you'll get a non-trivial amount of people voting for Binface either a) because you don't care about politics & think it's funny b) as "anyone but Farage" c) to treat it as a by-election because they think Binface won't take his seat and it'll trigger the 'real byelection' with their preferred party instead.
I think Farage will probably win, but it will be a lot closer than he would like. While they will make no difference at all for his hard-core supporters, the financial allegations will be discouraging for at least some of his voters and will reduce his turnout, all serious anti-Farage tactical voters will vote for Binface as the most likely protest candidate, and a nontrivial number of voters will vote for Binface just because it would be funny to do so - Britain is the country of Boaty McBoatface, after all.[0]
According to the bookies, Binface is currently 8/1 to win (about 11% probability), and Farage 1/8 (about 89%), with the rest of the candidates nowhere. There's probably something Bayesian you could do to estimate the probability of various margins from that, but it's going to be uncomfortable for Farage no matter what - winning over Binface by an embarassingly small margin will not enhance his image, particularly if there is going to be another byelection called soon after with the financial issue continuing to be in the spotlight. The only way this works out favourably for Farage is if he scores a crushing victory over Binface with an increased voter share relative to his previous election result, and I think the odds of that are slim.