Very helpful, thank you both
Using mixture's schematic, I have the NAS as "Host A" connected to successfully bridged LAN ports in my XP MCE machine that is also runnng Wireshark, and my BT HomeHub as "Host B". WiFi is switched off (adaptor disabled in the PC) for good measure.
Using it's IP address I can browse the NAS from the PC so it's alive and well and I can also reach my Homehub admin page and the internet too.
Homehub still set to block all LAN activity from the NAS' IP address that trys to reach the internet (and viccy verky) so time for some Sharking.
Stay tuned....