ok, so just an update....
Before I tried to configure the firewall rules as mentioned above but I noticed I was still able to ping the routers from each subnet
192.168.10.1
192.168.20.1
192.168.30.1
192.168.40.1
192.168.50.1
However by default I couldnt ping the devices on the other networks. eg. whilst I was on network: 192.168.10.1, I could ping 192.168.20.1 but not the laptop with IP 192.168.20.15 - I pressume this is normal behavior and the edgemax is designed in this way.
So my question I guess is, should I even bother to setup the firewall rule to prevent interLans as it seems it does this by default? I also assume each network needs to be able to see the router IP regardless of if its on 10.x, 20.x, 30.x and so on - So is it worth preventing access to the router's IP when on the other subnets?