Just to report back here, I had all my mods in the MODS folder and that was working fine (but taking a lot of space on my C drive as I added more mods, as Aquila-SmartWargames said earlier). I therefore moved them all to a newly created Data/Z folder (in my installation folder on the D drive) and I can confirm that that also worked fine. Seemed to take longer to load first time, but after that it seemed to be back to normal so the end result is good.