What I am going to be doing over August - on my extremely long list of things to do - I will be setting up two nics in the proxy server and I will connect the BT Router up to the second nic and the the first nic up to the switch. This will address the issue where the more clients added to the network, the slower the impact on the BT Router for loading webadmin pages.

As both of you have suggested using internal servers as the DNS Servers, I will have a look into this again. But I will check on spiceworks to see if anyone can shed any light as to why several clients Internet stopped working on the same day two years ago when I was using the Server DNS root hints. Would it be something to do with windows servers not being updated regularly. At that time I did not have WSUS setup. I do now. Maybe windows updates needs to update the root hints?

Could you elaborate on why a BT Router would be affected by traffic on the Lan Lonk. As far as I understand things, the BT router is a switch in the sense that it would only respond to traffic if the traffic was meant for it - unlike a hub. It is a router in that it would only route traffic to the outside world that actually needed to be routed and as for dns resolution - it should not be that onerous a task to resolve a dozen website addresses at any given time - its not like it has to resolve 500 addresses in one minute - given the number of clients on the Lan. I just cant understand why especially the wireless would impact the BT Router so much.

If I use internal DNS on the windows server, then I presume that there is no point in getting a draytek Vigor Router? If Dns will be done by the windows Server, firewall done by the Internet Box (although the BT router by default blocks most incoming connections) and if the BT Router is connected only to the second nic on the Linux Box - then it only receives traffic that is being routed to the Internet. In that case, I may not bother with the draytek router.