That's a puzzling one...
May be a bit of a stupid question, but do you own/have access to a wireless access point (such as a modem or router that supports wireless) for it to connect to?
Yep, I have a Netgear Wired/Wireless b/g router
I assume you do as you seem to know what you're doing, so:
Have you tried keeping it right next to the router? Have you tried switching the antennas (probably isn't gonna make any difference, they should find each other without antennas even when next to each other)?
It's sat within 50cm of my router and WiFi Analyser reports my WiFi signal 2-3 times stronger than others it detects in my area.
Have you tried resetting it to factory settings (you can do that from the hole under the camera as well as from the browser interface) and starting over?
Yep, I have tried resetting the camera, plus allowing my router to allocate the IP address, allocating a fixed IP address within my network range etc etc
Does the LED blink green when you pull out the Ethernet cable? If it does, approximately how many times per second would you say?
No the LED does not blink when I remove the cable.
Hope that helps, it's all I can think of right now.
Thanks for trying, maybe the WiFi chip doesn't like my router, it wouldn't be the first WiFi/Router miss-match ever.