All candidates are generally expected to attend hustings - where Farage would have been planning to attack the Labour / Tory / Lib Dem / Green candidates as part of his response to every question, hoping to get as many catchy soundbites as possible that can be clipped up for social media. He already set out his stall for this election being The People vs The Establishment, but that's not going to play out very well when the other candidates are clearly not The Establishment.Imagine if there was a debate between Farage and Binface, that'd be TV gold!
Instead I expect him to be absent, missing out on the opportunity for the soundbites, but also missing out on the comedy gold that would have resulted. It probably won't help his tag line though if the motley bunch of candidates do all attend, but he appears to think himself above such an appearance - some might say that is very much a sign of being part of The Establishment.