Hi Luke,
Thanks for your reply! I think I understand now. I didn’t realise that the plugin had an ‘option’ to automatically send the sitmap url to a virtual robots.txt file — which was generated by Worpress itself.
The text at the tickbox in the plugin settings says;
# Add sitemap URL to the virtual robots.txt file.
The virtual robots.txt generated by WordPress is used. A real robots.txt file must NOT exist in the blog directory!
Reading this, not really knowing what a robots.txt file does, was confusing. I will now uncheck/disable this option and use a separate plugin for robots.txt (including a sitemap url), like you explained.
Regards,
Mark