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I disagree.
I do think they will suffer from lack of infrastructure, but the streams of dodgy cash they can call on will mitigate that a bit. They peaked at 20%+ in the polls back in July and if Brexit doesn't happen they will hoover up the rest of the 30% who favour no-deal from the conservatives. The tipping point to start winning seats is somewhere around mid to late 20's IIRC. No-one really knows what would happen in a 4 party race but I'd be pretty worried.
Even in the case of no Brexit there is no way the Brexit party will be become any kind of major player. They couldn't even win in Peterborough which is a Brexit heart land, they have no party infrastructure to fight a general election in any real way.
They might be second or third in a shit load of constituency and get a load of votes but like UKIP before them they'll fail to make any real impact in a first past the post system.