Ahh, that's brilliant @pennsif, greatly appreciated :)
I've managed to get the brain-freeze to ease and redone the design (though in principle it's the same as diagram #2). I'm trying to keep the design super simple (though you wouldn't think it by how I've struggled today lol) and inexpensive. So when things are at that point, I will quick-test the below set up and all being well, implement it. If it goes pear-shaped then I will follow your advice and give the Discord channel a go :)

Many thanks again,
Rob.