By "Extenders" I presume you mean that they are powerline adaptors.
Unplug the powerline adaptors from the electrical sockets and disconnect the Ethernet cable from the Homehub to the master powerline adaptor.
Carry out a factory reset of the Homehub by pressing a pin into the recess button on the rear for about 20 seconds.
After it has restarted plug the powerline adaptors back into the electrical sockets and re connect your master powerline adaptor by Ethernet cable to the Homehub.
Thanks everyone. I tried using an ethernet cable from router upstairs to TV hub downstairs. This is not a good long term solution as the cable only just stretches up the stairwell. This worked superbly however. I then took the TV hub and extender upstairs and used the extenders. Again, this worked superbly. Have now gone back to original set up and we are back to orange and yellow flashing lights on extenders.