Thanks Matt, I have been restarting the router daily as it gets switched off at night when I turn off the PC, I turn off at the wall socket, this made no difference
In sheer frustration I did another Google search about the D-Link router to see if there were any settings that I was overlooking and came across a thread on the Talk-Talk forum and someone suggested a hard re-set of the router by holding in the re-set button for up to 30 seconds, I tried this but the router refused to fully start up afterwards. I used the power switch to restart it and success, I now have wireless connection ! I did not need to do anything else, it configured itself automatically. The re-set button is different from re-booting or restarting the router, it must be held for at least 20 seconds to do it's job, I held it for 40 seconds to be sure.
After all that frustration and going down the wrong route of thinking it was a driver issue after a Kernel update, then re-installing the OS, drivers and all my software etc, it turns out to be a router issue !
I wish there had been an easier way to discover this !
Problem now solved.