The Sun has consistently been the biggest daily in the UK for a long time, and I would suggest at least some of the parties have a majority buying that paper, historically the Mirror which comes in 3rd would be considered a more leftist paper (as was the guardian itself) and so would be much more likely to be a favorite amongst Labour voters.

The Mail hasn't had daily sales over 4 million this millennium. But since you apparently overestimate the guardians sales by 100% too I guess the point you're making still stands.

http://en.wikipedia.org/wiki/List_of_newspapers_in_the_Unite...