Many thanks for this Andrew.
I eventually realised - thanks to your helpful tips above - that the image was actually loading in the browser, but that the image state reference variable/ active state value were cancelling it out, so it wasn't displaying. I think I copied this from the moonlight sampler - but may have screwed it up... Clearing this allowed the albumcover pic to display in Chrome, and on my iPad...
I'm pretty technical - my job involves constant connectivity & network challenges, but more the nuts & bolts of it all/ fault-finding on my feet! - I've never really needed to learn any programming languages/ web design, so I'm a total amateur at this...
It's good to have a challenge and learn new things though!
Many thanks for your help - much appreciated!
Ben