[lambdaone]

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.

[0] https://en.wikipedia.org/wiki/RRS_Sir_David_Attenborough#Nam...