The pricing in the Software Centre and in the Dash is in USD. I don't live in the USA so this is not relevent to me. Is it possible to change to GBP or even EUR?
It does not look like this is possible at the moment (however, I might be wrong). There is however a bug on the subject: https://bugs.launchpad.net/ubuntu/+source/software-center/+bug/1002647
You could help out by going to the bug and click on "Does this bug affect you?".
It should be fixed! =)