Ah, bingo! Thank you so much, Tom. That was it. I completely forgot about spot metering - tried all the different settings and most of them worked but that's the essential I missed. Yay!. I knew it was something simple that just slipped my mind. I had it set on average metering or center weighted (can't remember what the symbols are right now) and didn't go back there for a long time.

Tom, you're a genius! 

 

Liam