Read up your rights under that, especially your right to get all the data that they hold about you for £10. If that data includes the history of your web browsing, then certain consequences follow; make sure you're using a proxy even for innocent activity for a while before you submit the request. On the other hand if it doesn't and they subsequently challenge something that you have posted on line, they will be in BIG trouble for failing to reveal that they knew your browsing history.
Assuming you are under 18, your parents' role in this is more significant than yours. If you are over, it gets far more interesting!