OK, let's look at Question Time... Since the 2010 election, UKIP has been represented 20 times despite having 2 MPs at most. Nigel Farage who has never been an MP and is barely an MEP based on his contributions has been on 11 times.
Put another way, based on the 2015 post election parliament, UKIP has 0.2% of the parliament seats and 3.7% of the appearances. Data from
here
So yes, Brexit is over represented based on the balance of parliament (interstingly, SNP is massively underrepresented)