Hi,
My mum was having problems with TalkTalk, and their apparent blocking of games over the internet at peak times.
The one thing that i would suggest above all others is to write very strongly worded letters to the highest person you can within TalkTalk, and copy them, with a covering letter, to OFCOM, explaining all the troubles you have had. If this doesn't provoke a positive response, i don't know what will.
Martin