Well, with the help of your grand advice and encouragement we've decided to switch from Orcon to Snap... sweet!
At present we use an Orcon-supplied Cisco small business router, so that'll have to go.
The current setup is:-
ONT-> Cisco SB router (in bridge mode) -> Ubuntu server as firewall/DHCP server etc -> 48-port GB switch -> LAN
I'm trying to determine whether we will do OK with the standard Fritzbox, or if we should grab our own Cisco box at this point, or (just maybe) we perhaps don't even need a router box in this setup and can simply configure the Ubuntu box to talk with Snap directly.
If its relevant we are pushing through up to 100GB/month, with quite a high portion realtime video links, some VOIP.
Any advice would be very much appreciated. Thanks guys!