It's not broke so I'll be leaving it alone.
The Duo and the Zgemma will shortly be in different rooms with a universal feed for the Zgemma and the Unicable continuing to supply the Duo. The LNB is a GT-Sat GT-S1DCSS24.
The multiswitch installation predates the present arrangement by 10? years but I understand the opportunity you've suggested. I'll bear it in mind for the next time something breaks!
I'll need to think that through and won't be doing anything until I'm sure I've got my head around it. Eight concurrent recordings is currently sufficient!
We're coexisting quite nicely at the moment though I've a real dislike of the remote. The Vu+ remote is far more user-friendly, something which is important as the Zgemma is destined for my tech-phobic wife.
Thank you again for your help and patience. I really have appreciated it!