I'm just not following your logic at all. And Nigel Farage isn't the head of UKIP any more (which isn't to say that he wouldn't come back if any attempts to stop Brexit happened), but UKIP had the best general election ever and had the most traction they had just prior to the Brexit vote - arguably their absolute peak and I believe they had one seat in the commons, with maybe around 12% of the overall vote. The very two party system you are talking about pretty much guarantees that a fringe party like UKIP never gets much power. One vote in the commons when they had over 10% of the overall vote. Any form of proportional representation or other system would have handed them a lot more power than they got. They would never manage to get to 30% of an overall vote - for information the Labour party managed to get 30% of the vote in 2015 that is how many more votes UKIP would need. In the last general election UKIP didn't even get 2% of the overall vote so I just don't see them reaching anywhere near 30% ever.