After non voters and transfer voters have been eliminated, only a quarter of the population of the UK has representation by one of the three largest parties, "

What "transfer votes" is he talking about? It's FPP.
"...quarter of the population"
hmmm.whats he actually talking about? In the sentence he claims to have eliminated non voters from.his arithmetic but then without so much as a full stop apparently adds them back in?

-Again, I don't know where these figures are coming from.

The actual figures were widely available:

Last time I looked Labour got 33.9% Tories 23.6 % and Lib Dems came in at 12.1%. That's about 70% of the vote.

The representatives they got from that vote are in fact well out of kilter with the % of vote at about 93%. So in terms of voters the opposite of what he says is the case.