@chrisjmuk
I get the impression you're heading in the wrong direction. With IPv6, most ISPs provide multiple /64s. I get /56, which contains 256 /64s from mine. I then assign a /64 to wherever I have a network. For example, I have 1 each for my main LAN, guest WiFi, test LAN, Cisco router and OpenVPN. I suspect you're still thinking in terms of IPv4, where is was necessary to use a hack, NAT, to make up for the address shortage. No need for that nonsense on IPv6.