//The internet speed is not very fast. Do I change providers and is this easy?//
What speeds are you getting.? Changing ISP is straightforward; but initially you could be out of pocket if you are under a specific time contract.
You are right to walk away from Talk Talk. Speak to Orange there could be a simple answer to your problem. Make sure there are not any loose cables connected to your equipment and check your speeds before proceeding further...... A click on the following will enable your speeds to be established and an indication of what others are available in your area, along with costs involved.:-
http://www.uswitch.com/broadband/speedtest/
Hans.