When you get through to Talk Talk make sure you get the name of the person you speak to, and treat them as your friend. Their telesales agents are always extremely busy and much of their business is handled by Indian call centres.
If you can personalise your business with the agent, eg. ask them about themselves, eg. what their having for lunch, what was the traffic like on their way to work etc. I've found they are more likely to prioritise your business and return your calls.
They are cheaper than BT. Fact.