Hi adrian at abcdesign co uk,
When you switch to any of these VR Cam Render Settings, can you see the Global Illumination rendering option in the list? If not, go to Options [Render Settings] and enable it, set the settings as before. (COPY and PASTE works as well!)
Eventually check if the IR-Cache is working for the scene.
Please have a look at the clip below, it is one minute, and you can download it for private use. UHD for best viewing experience :o)
https://www.amazon.com/clouddrive/share/vRC5QFRi5KZOy5ACxSV084MUfJtZqJD8eR1bWtXxlx3?ref_=cd_ph_share_link_copy
I hope that is working for you.
All the best