The blog displays as being in the sub folder, but is hosted in the blog.stitchandprint subdomain and uses the described reverse proxy arrangement to serve the blog content up in the sub folder to enhance the SEO value a bit. This was working fine despite various teething troubles and we were able to access the wordpress back end, create new posts and edit old ones.
Since we renewed the expiring simple ssl certificate and upgraded it to a wildcard certificate to include the blog as well, we seem to have had nothing but trouble. We are back to the situation where wordpress is giving errors when we launch it. When it does open, it says there is no SSL certificate - when there is. On opening the post editor, the editing panel is completely blank. I believe the website is still running on version 7 of Deconetwork and I am unsure why this change has happened.
In addition have had an outside guy look at this. For us it seems to be a DNS conflict because our blog is hosted on a subdomain of the primary domain we've mapped to the deconetwork servers while the blog is hosted on our own hosting company's servers!
I migrated the blog content to another domain completely and backend is now working fine. It would seem that the old setup, with the blog on a subdomain of the main site, is no longer viable. Having tested the new arrangement on a spare domain of mine, I will check with Richard that he's happy and migrate it to one of his spare domains, once hosting is created for it.