"I might seem radical in the context of US politics, but until New Labour reared its head, my views were pretty much represented by one of the UK's 2 main political parties...that's the difference, I think"

Naturally it is a difference - you cannot compare the politics of both countries in those terms because of the different situations and the fact that the meanings are also different between countries. The histories of both countries and how they treated people are also a factor in where the "middle" appears to be. Both countries have made considerable progress, but there is still much work to be done in both. Racial relations in the UK are not very rosy from reports that we hear. Our own history is pretty evident as well, which makes the election of Obama seem that much more "liberal" considering that 40 years ago he would not have been allowed to vote in some parts of the country.

At the end of the day, there is no badge of honor to be worn for being "liberal" or "conservative". Discussing which country is more "liberal" is akin to pulling out a ruler and seeing whose is longer. Actions speak louder than figures.