Waveshare - Brilliant!

Well, my little problem with Waveshare 7" screen has been fixed in 24 hours!

Thanks to exemplary e-mail customer support direct from Waveshare in Shenzhen, I was told to try and reinstall a ribbon cable at the back of the screen.

The red-marked cable socket.  A lift tab above the top of the red box isn't clear or present in this image, so make sure you lift it before removing and replacing the ribbon.

If you end up with a similar , flickering, banded or non-functioning Waveshare screen, the first thing to note is how to remove and replace the ribbon.  DO NOT pull it out, although you can do this without damage, but you won't get it back in.  First, you need to lift the black hinged tab at the back.  This releases the contact clamp, and you can easily remove and replace the ribbon now.

After this, the screen worked perfectly.

For all the popular criticism of Chinese products, you would do very well to find anyone in the UK providing such rapid and helpful responses. 

Well done, Waveshare!