"so never agreed a contract with them."
If you were informed of the move and decided to carry on using them then you have agreed to their contract.
Why cancel a DD as this is you cancelling the contract (without notice if applicable)?
Were you initially told that there would be a cost, from yourself, for the engineer's visit? If so many engineers have been sent then it should be obvious to all parties that the main connection to the CAB/exchange is damaged or incorrectly connected so no cost to you whatsoever.
Unfortunately this is the issue with TV over the internet. Any numpty can cut through a cable with their JCB and then it depends how long it takes to reconnect.
Was Eclipse Home Option 1, VM 2Mb & O2 Standard
Now Utility Warehouse (up to 16mbps) via Talk Talk