Whatever you do, don't got with Talk Talk! They are consistently one of the worst performers.
You will definitely get faster speeds (you're pretty near the exchange). Although it depends on what is available at your exchange just how much faster you can get. Some ISPs provide LLU services (this info will be listed for your exchange on the Samknows site), which may give you faster speeds than what you've listed.
I know with my exchange, if I do checks to estimate my connection speed it'll tell me 6MB because BT (or any ISP that uses BT's equipment) can only offer me up to 8MB. However I went with a LLU provider (who have their own equipment inside the exchange) and so I can get 12MB (advertised as up to 16MB).
However, if you don't really need the speed, because of the additional cost of needing a landline your are probably just as well just sticking with your mobile broadband, until such time as you need the extra speed.
Cheap ISP's like Talk Talk may seem attractive, but speed and reliability aren't very often heard in relation to the service they provide.