I downloaded a 100Gb in a MONTH, not a week.
Also if you take a minute to think about how bandwidth works you'd realise that a capped download rate is no different to a total cap. I could sit down with a calculator and work out how many Mb/s I would pull in a month but frankly I can't be bothered (I'm also rubbish at maths so I'd get frustrated!).
No... Theres a big difference between usage allowance and download rate...
Usage allowances are a set limit on how much you're allowed to download before you have to pay for more, regardless of download rate.
When you're on an unlimited package, it only means you you have no limit regardless of download rate... Which means you can still download as much as you want but at a restricted speed.
BTs T&Cs state this fact, they're still providing you with an unlimited service...