It all depends if the votes for the Brexit party are spread evenly throughout the country or are concentrated in particular constituencies.
It's an unfortunate result of our first past the post system that, for most people, it really doesn't matter if they vote or not as they live in safe seats that haven't changed hands in decades.
General elections are decided in the relatively small number of marginal seats where a few hundred or a few thousand people voting differently really will make a difference.
Take the 2015 election for example. We all know the result but if that election had been run under PR in the same way that the German elections (or also the Scottish elections) are held then both the Conservatives and Labour would have had a lot fewer seats.
There would have been more Lib Dems and more Greens but the real winners would have been UKIP with around 80 seats. They would be the third largest party and the likely outcome of the 2015 election would be a Conservative/UKIP government supported by the DUP.
Just imagine what that would have looked like. Under PR, Nigel Farage would probably have been Deputy PM (like Nick Clegg) since 2015.
So, it all depends on how their vote is spread. If it's concentrated in particular areas then, yes, they will get MPs and may well be decisive in who forms the next government. If their support is spread widely but thinly then they may well end up coming second in many areas but not winning. But by taking a lot of votes they will alter the normal sort of results and previously safe seats may no longer be safe.
Likewise Lib Dems may end up coming second in a lot of areas and also upsetting what are considered safe Labour seats. So who knows what is likely to happen.
One thing I will say is that this Thursday's by-election in Peterborough could be very interesting.
For those that are unaware, Peterborough has generally been a very marginal seat and usually votes the same way as the country overall (although in 2017 it was really close and went Labour by just 607 votes).
The Labour MP was sent to prison earlier this year and there is to be a by-election to replace her.
The city voted 61% leave in the referendum and in the European elections voted overwhelmingly for the Brexit party.
38% Brexit, 17% Labour, 15% Lib Dem, 11% Conservative, 11% Green (for comparison, the national figures were 31% Brexit, 14% Labour, 20% Lib Dem, 9% Conservative, 12% Green).
So does Peterborough hate immigrants? Well, no.
Peterborough has always been a place where immigrants have settled. (Even back to the times of the Napoleonic wars). After the second world war there were many Poles and Ukrainians that settled in Peterborough and in the 1950s Peterborough became the home to one of the largest concentrations of Italian immigrants in the UK.
A legacy of this, for example, are the Orthodox and RC churches and also the RC secondary school that was specifically set up for the children of Italian immigrants by Peterborough council.
Later, the city became a "New Town" and expanded rapidly with many people from throughout the UK moving here (although I think most came from London) and later in the 1970s there was quite a large influx of Asian refugees who had been expelled from Uganda by Idi Amin.
So, Peterborough has a long history of immigration and, generally speaking, there haven't been any real problems.
However, over the last ten years or so there has been another enormous growth in immigration, this time from Europe. The local council estimates that one person out of every eight living in the city is a European migrant.
These migrants are generally quite young and fertile. Around 50% of all births at Peterborough hospital are to mothers who were not born in the UK. The largest group are Polish. This then feeds into rapidly increasing demands for extra school places which are causing strains on class sizes in the city.
Even anecdotally, walking down the street if you see a young couple with a child it is more likely than not that they will be speaking a language other than English.
That's not to say that the schools are not coping as best they can and even doing well in some cases (although the city as a whole performs below average in the league tables). An example from the Guardian:-
The school where they speak 20 languages: a day at Gladstone Primary
Not one pupil at the Peterborough school speaks English as a first language. But, despite the challenges, it has just received a glowing Ofsted report. The Guardian spent a day there
But it really has been this massive increase over recent years (along with effects of austerity) that have really changed things and how many people perceive the situation.
Even The Guardian, who are very much "Remainer Central" when it comes to Brexit have reported on Peterborough a number of times over the years, the latest being just today:-
Peterborough prepares for byelection that could elect first Brexit party MP
A decade ago it was the UK’s fastest growing city, but hit by cuts and buy-to-let, support for Nigel Farage’s party is high
On Thursday, voters in Peterborough will take part in one of the most intriguing parliamentary byelections in recent memory. The constituency saw a knife-edge duel between Labour and the Conservatives at the 2017 general election and at last month’s European poll, 38% of voters in the city backed the Brexit party. A first seat in the House of Commons for Nigel Farage’s party is a distinct possibility. If that happens, it will send tremors through middle England, of which Peterborough is typical in many ways, not just geographically.
I live in Peterborough and, quite frankly, the Brexit Party candidate is the only one that I've actually heard from.
This is an important by-election and the Conservatives and Labour can't even be arsed to get off their backsides and ask me to vote for them. Come Thursday, I'm much more likely to vote Brexit than anything else.