Use these calculators to examine your broadband usage:
http://www.simplyswit...usage-calculator.aspx
http://www.which.co.u...and-usage-calculator/
https://ben.cheetham....data-usage-calculator
http://www.broadband.org/usage_calculator.html
(NB: Try them all. You're likely to get different results but at least you'll get an indication of what it is that's taking up the most of that 10Gb figure).
When looking elsewhere for a decent deal, remember to google to try to find out the 'contention ratio' for each ISP which you're considering, together with their 'traffic management' policy.
The contention ratio indicates how many other users you'll effectively be sharing your connection with. (The more users there are, the slower the connection speeds you'll get). Most budget ISPs have a contention ratio of around 30 to 1, with some providers (such a Virgin Media) only offering a 50 to 1 ratio. Ideally you should be looking for a contention ratio of 20 to 1 or better. (My ISP has a 7 to 1 ratio, but I pay 'business prices' to get it).
All ISPs (except BE Broadband) deliberately slow up certain types of internet traffic at peak times, in order to ensure that (for example) people who are file-sharing or video-streaming don't hog all of the available bandwidth, to the detriment of others. It's worth knowing what the policy of an ISP is before you sign up and then find that your internet service slows to a crawl at busy times!
Chris