Think I've figured it out... had a problem with the Wordpress htaccess file and for each post/page/sitemap etc. it was showing a non-css'd version of my main website homepage instead of that post etc.
Googlebot has obviously gone to the non-css version of my homepage but at the "correct" blog post address, then found document-relative links that it then can't follow...
I'll go through and mark all 404's as fixed and hope they aren't re-crawled. In the event that they are, what can I do to get rid of them as there are 2,666 404's in my Google Search Console and I have seen a drop in rankings...
Cheers, Paul.
