Ok, we're up and running with images on the mobile version. I deleted them all, published the (image blank mobile variant) website. I then looked at my CDN settings in IONOS/(1and1) and made a few tweaks. I was in there to purge my chache but also changed the following settings;

I changed 'auto minify' so that it was doing JavaScript as well as CSS and HTML. I also put this to 'on';

Mirage™ (Intelligent Image Loading)NOFFImages on your website are resized to fit the visitor’s device, and are loaded only when the visitor scrolls to their location.

I also changed this to 'lossy';

Polish™ (Image Compression)*:Compress the image files for faster image loading.
For immediate results, you need to purge your cache.

And I put this to 'on';

Railgun™ (Quick Loading of Dynamic Content)**NOFFImproves the loading performance for website pages with dynamic content.


Somewhere, somehow something here worked! Hope this helps anyone else.
Thanks for all your help Gary.
Yours,
Robert