Certainly all papers have a bias, as does all media. We have to be alert and compensate for that. But taking your link, for example, if you look at the percentage of people who think the Guardian is 'very left', four of the nationals are 'very right' by a greater extent. Indeed, even the fifth - the Times - is very close to it. (14% rather than 16%). The next paper, the Independent, drops dramatically to 4%.

Conversely, if we look at the Daily Mail, more than twice as many - indeed only a little less than three times as many - think it is 'very right' than think the Guardian is 'very left'