Unfortunately changing HDMI cables didn't work. I suspected it wouldn't because if the HDMI cable was faulty it wouldn't have been able to play a pre-recorded DVD movie to the TV, which it can do.
This statement is not totally correct. I had borrowed my friend's HDMI cable, and connected it while the machine was still on, and it originally hadn't worked. However, I had then switched the machine off and forgotten about it. When I switched it on again some time later, it took an extra long time to boot, where the display kept saying: "Please wait". Finally it turned on and worked properly using my friend's HDMI cable which was a different brand to mine. I think I should have had the machine turned off when I changed the cable, since when it re-booted it seemed to re-set something.
My friend then told me when he used my original HDMI cable to connect his Panasonic, it worked initially, but when he moved the cable just slightly, the picture switched off. If he moved it again the picture came back. He did this several times with the same result. So obviously the cable was faulty.
I then took my original cable back to the GGs, and they replaced it with a Platinum HDMI cable, ( which was almost double the price of my original).
That was today, and my machine has worked fine since then, and this seems to have fixed the problem. However, before I can be absolutely sure, I'll give it a few days of operation.
As a point of interest, my original cable was "gold" quality plugs and the cable itself was made of a soft silicone type of material. Ironically my friend's cable was a cheaper "silver" quality plugs, and a blue less flexible cable,
Thanks for all the input guys. I was on the point of taking it in for repairs, but all going well, I won't need to do this now.
Cheers Bernie (Poppabear)