Hi I have only after signing up to my isp (talk talk) realised that they do not actually allow you the full use of the internet connection i.e. they block certain traffic and in a sense spy on you by using deep packet inspection techniques.
I have found a site that tells you which isp's do this so as to ensure you do not fall for this.
It seems many major uk ones do this except sky.
Feel free to comment/critisize as my knowledge on this topic is very limited will appreciate any feedback. http://www.azureuswiki.com/index.php/Bad_ISPs#United_Kingdom