I don't see the problem with talktalk. I've tried a few times to swtich my folks across their deal does seem okay and my folks's exchange is TT LLU or BT adsl.
They get 6mbps now. But when I had a flat in 2011 I got 13mbps from Be over LLU and I was further away than they are from their exchange so they could well get double too.
There's also a very good chance not a lot of people are on it and even if the whole exchange was that would only be 1000 people.
The problem with TalkTalk is they don't have BT Sport.
Ok, they have Sky Sports, but it's £30/Month. Plus I think their Youview box isnt as good as the Humax model offered by BT