There's wireless here now. Fully open, unencrypted and advertised ESSID "FitzPublic".
Note to self: (for when router inevitable dies and I'm back in this mess)
HyperWRT + firewall script of:
iptables -I FORWARD -s 192.168.1.1/24 -d 10.0.0.0/8 -j DROP
... seems to do the trick.