So after taking the advice here, I just signed up for the free trial of Roon. A very impressive start. It found my 861/ID41, the music on my MC200, all my Bluesounds as well as a whole bunch of other endpoints that I hadn't considered (I had no idea I had a speaker in my keyboard!)!! So I now have it running 12 Bluesound zones, my Meridian system, my main PC, my amp in the cinema room and a couple of Google Homes. Although it didn't seem to find my single sonos soundbar.

But one thing I don't understand. Why do I need a Nucleus? From the Roon website, the Nucleus doesn't support more than 6 zones (although my PC seems to?), so I would need a Nucleus+.
I've tried searching through the forums, but the only advantages I can see mentioned are simplicity and stability. But through the PC its incredibly simple. My PC is on 24/7 anyway, and even if it updates I can still use the BS app to control all my non-Soolos zones.

What am I missing ?

thank you !!

Audio: DSP8000SE upgrade, MC200, 818v3, Tidal, Bluesound
12 Bluesound zones, 1 Sonos zone, Roon
Movie1: Sony VW-790ES, 145” screen, Pan DMP-UB900, Oppo BDP-105D, Denon AVRX7200, Artcoustic Spitfire Subs, SL 8-4 (fronts) , SL4-2 (rears/sides), SL4-2 (4 ceiling)