On sky's LLU unlimited package for £7.50 now or £12.50 without line rental there are no limits.
Sky is the only ISP to have NO fair usage policy or traffic management. This means absolutely no users are restricted for downloading too much, even the top 0.000001% of users are left be. T
Other ISPs such as O2 on LLU do not limit anything currently but they do have a Fair usage policy that they could decide to impliment at any time. For all we know they could decide to slowdown their top 1% of users next week (unlikely, but possible). With sky this couldn't happen as there is no fair usage policy what-so-ever. This is why sky have been able to advertise as the only 'truly' unlimited ISP.
As for torrents, they go at the speed of everything else. Nothing is prioritised, you get your full sync to do whatever you like, the way it should be. If you want to use P2P you can, if you want to download from rapidshare you can. I used to get 1.8 mb/s on torrents with sky.
Moved to VM since as I have a slow sync where I live now... Not so good.
If no throttling ect you will see speeds of upto your normal max throughput, so if you can d/load at say 19mb that's what you could get using u torrent, but this will depend on the torrent file, how many seeds leechers,and the speed being provided, and which peers /seeds you get connected to, lots of factors dictate how fast a torrent will download, as a test try download the open office app via torrent, should max the connection out