you can only sue for...
In the UK, when it comes to sueing for money, the first question you have to ask is, what have our (the film company sueing) personal loses been...
Well, if someone downloads, for free (illegally) a copy of a DVD, the answer is a difficult one. The defendant could easily argue that becuase its a DVD his friend owns, that he would have just borrowed it anyway, and therefore the loses are £zero. You could also say the the film company has lost the cost of 1 x DVD royalties, which is going to be £5-£10? You then have to add on lawyers fees, etc.
However, if you upload while you download (the standard setting for most p2p/torrent programs) then you've distrobuted the DVD (just parts of it, maybe) to possibley thousands of people. So suddenly the film company has lost thousands of potential DVD sales, directly from your actions, ie 1000s X £5-£10? Then add on the laywers fees etc.
You can, of course, tell your torrent program (i've heard) to not upload any data, and therefore you're not distrobuting any data at all.
Thats as i understand it, anyway.