Sorted!
Thanks for the link above. My problem was not solved by what was listed in there but it did lead me on to find the issue. wp was uploading my images not into an uploads folder within wp-content, but straight in to the wp-content folder. Therefore wp just couldn’t see the images. No idea why it was doing that, but just was. Overridden that now though.
Thanks for your quick replies and help with this – very appreciated.
Many many thanks,
Jon