Sorry this has taken a day longer than expected but its all just a lot of cables to me.
Anyway after turning the mains power off (I think it was 4 times) and trying to reset the system, it finally worked and I got the flashing I was looking for.
However when I started the system up the centre speaker worked (for about 3 hours), but the left front speaker did not work.
I reset again and got all the speakers working (for about 10 minutes) then the left speaker died again, then the centre speaker - I did this a number of times and got a variety of "not working" combinations.
Basically the Denon receiver was in need of new parts and Denon have taken it back (when I see it again is anyone's guess, but that is a problem of living in a small country).
That all aside, thanks for your help and I will now rate your service in the positive manner it deserves.
Denon replaced the unit with a new one (newer model), which worked perfectly straight out of the box (but so did the last one) - I just hope the build quality is better.
Nice to be able to hear all the speakers again.