The polls are questionable because of the layers of voters. In highly urbanized areas....the vote will still go to the Tories and Labour to some degree. In rural regions....it’s probably going to be 5 votes for each BREXIT Party to each Tory vote. It’s really telling a story over the division of society in the UK.
I project the Brexit party to collapse by 2020 - it’s a single issue “party” which has made no attempt to get party members, just putting up people for election to the EU parliament. To win MP seats it needs to prove what it can do for local, more tangible matters