You should get your parents to look into it, because 2MB is the slowest they do now - 2MB, 4MB and 20MB are the options.
The upgrade should be free, so it won't cost any more per month - but you may as well get what you're entitled to.
Enter your postcode
here and see what you can get.
If you're already on cable broadband, you may be able to trigger the (free) upgrade
here. But make sure you check it through with your parents... I'd hate for you to click something which upgrades you to 20MB without realising!