So the new forum was back originally
www.clanuk.org.uk, then I got the clanuk.co.uk domain back so switched to using that.
The imported legacy smilies were originally hosted on clanuk.org.uk, so the forum config has that URL and path in for each, so even though they were copied over to the clanuk.co.uk site the config is still pointing to the old domain. Instead of fixing the config for god knows how many images I just put some cloudflare page rules to redirect traffic from the old domain to the new because I still own both.
So the config is still wrong but Cloudflare is handling that for us. It's a bit lazy, but it works, so meh