Sky seem to be going down the route of blocking public p2p sites like piratebay as opposed to lettering (although those sites are still available via proxy), I have never heard of anyone being lettered. Apart from Americans (who are on the strike system) and even then it seems release specific. The most recent I heard of was the sparks release of the new wolverine movie which seen loads of people lettered. I really cant see any UK ISP's sitting on torrent swarms cherry picking out their own IP's. Even if that does happen most will start using proxy's or a combination of a proxy and seedbox then opt for FTP.
I would be most concerned if any ISP was "watching" & closely monitoring internet traffic.
I have found sky to be a devil may care ISP, compared to the likes of pipex and aol who in the past cancelled my service due to excessive downloading, adsl24 (i think that was their name) were also pretty awful.
Even if they do throttle at times almost all torrent clients allow you to set a schedule, combine that with something like auto irssi and you are set. If leaving a PC on all night is an issue then a lot of NAS's can be set up to do the 'biz' for you and you can control your downloads via smartphone.
Legal downloads of course