Many thanks Hans, much aappreciated. I see where the 0100 comes from - it's 01 plus the MAC address.
I tried what you suggested, but I got a bit lost! My current DHCP pool is 192.168.1.201 to 192.168.1.250, though in reality it doesn't need to be that big (20 addresses would be fine). Looking at your example I need to create TWO pools. Are you able to advise me on what the network and host settings could be? I tried entering