Thank you so much for taking time to reply. My first job of the day was to come on here to answer my own question in case anyone else encounters this - but you beat me to it.
Late yesterday, after much searching the internet with no luck, I realised it must be down to the printer because it was happening across all applications, not just Photoshop.
So I contacted Epson’s support chat online - I very quickly got to a human agent who knew straight away that I needed to download the driver for my printer directly from Epson.
I then had to uninstall my printer and reinstall it.
What had happened was that my Mac, for some inexplicable reason, had reverted to using Apple’s own generic print dialogue system.
I have no idea why that happened or where the Epson driver I had originally installed had gone - because when I checked the supplies and options section under printers and scanners as directed by the agent, there was no utilities tab showing.
Once I had installed the Epson driver and followed the agent’s instructions for ensuring it was active, all the previous colour control options were there again.
Thank you for responding to my question though - I really appreciate your time in doing so.