I was with Onetel for a considerable time, and eventually they were taken over by TalkTalk. Because I had heard so many dreadful stories about TalkTalk's service I resisted all their attempts to switch me over. But inevitably I eventually did so and have been on TalkTalk since last July. Well, in my case it has been totally painless and everything happened exactly as it should. Financially it must be unbeatable: I now get broadband, with a very generous usage allowance, telephone line cost included, and free phone calls 24 hours a day, 7 days a week, including 36 overseas destinations - virtually the whole of Europe, USA, Australia, Canada etc. The cost of all this is just £20.99 a month - just about half what I was paying Onetel and BT for a much less comprehensive service.
So while I might just have been lucky, all I can say is, this was the best move I could have made.
Regarding the tv, I have a freeview digital tv which copes with all I could possibly want to watch.