I've had a look in the bookmarks.html file and there
are some references in there to images but they're not in any format that I recognise.
They're all listed as:
data:<
insert massive string of numbers and letters here>
I've found a favicon picker
HERE which allows me to delete the offending articles and then replace them with icons of my choice, the problem is that when I revisit the site it doesn't save the favicon for that site any more.
What a pain this is becoming

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Ok, I take that back.
If you delete them with the favicon picker extension and then revisit the site it
does put them back
Looks like that's a way of sorting it out.
Thanks for the help