If you're leaving TalkTalk give yourself plenty of time and expect problems! Not just my experience (I had to threaten legal action in the end) but they are usually at the foot of any customer satisfaction league. However, I expect you'll be glad when you do.
I am now with O2 (landline and broadband) and more than happy with them; bill for line rental (including unlimited calls) and unlimited broadband (I get around 10 Meg speeds) is around £30 a month depending on how many 09 calls the missus makes. If you get a cheap SIM card from them you'll get a few quid off per month from your bill.
Ll