Conservatives polled 8,781,932 votes winning 210 seats = 41,819 votes per seat
Labour polled 9,570,458 votes winning 349 seats = 27,423 votes per seat
Liberal Democrats polled 5,981,509 winning 62 seats = 96,476 votes per seat
That could just show that the Conservatives always have bigger winning margins in the seats where they win.
Imagine a 2 party system. Party A wins 49% of the seats with 100% of the vote in each seat. Party B wins 51% of the seats with 51% of the vote in each seat. Party B would win, despite only getting around 25% of the popular vote. First past the post, innit.