Inline image transform using Matrix field for image quality?
Aha!!! Got it working at last!!

As I was using Live Preview, even though I was set to Dev Mode for any errors, they weren't showing in the Live Preview pane (maybe that should be a feature request?).

As soon as I tested it out on the live page I saw an error and it told me to place parentheses around an expression so I did this instead :

quality: (block.quality.value) and all is good with the world now!! :-)