On the bias at the heart of the First Past the Post electoral system:
1992: Tories had a lead of 7.6% over Labour in the popular vote, but won a majority of just 21 seats.
2001: Labour's lead over Tories is 9.3% - majority is 167.
In the next election, if the two parties had a similar share of the vote (around 30% each), Labour would win 111 more seats than the Tories. For the Tories to win the same number of seats as Labour, they would need to beat Labour by 6.4%.
So, lucky for them they have a rather large poll lead at the moment.
How does that work? Two reasons:
1) Average electorate in "Labour" seats is smaller than in Tory ones.
2) Labour wins a lot of seats with small majorities, the Tories stack up huge majorities in the seats that they win, meaning Labour get a better return of seats for smaller national votes.
Democracy... it's all about how you get elected eh?