Update...tech support have been helpful at D-Link but the problem remains.
I have updated with all the latest downloads and the problem is still there.
Last "fix" was so assign a static IP address to the router but it disconnected again last night when left "wireless", as soon as I connected a LAN cable it worked. Tonight I will leave the cable connected...tomorrow I will smash a router and feel much better! No seriously, it is frustrating and I will get to the bottom of it.