I finally got the time to put together a demo video:
The client is connected to the laptop with a USB connection. However, the client does all the positioning calculations, the laptop is just displaying the node positions and the current client position.
Averaging is turned right up which is why it takes a little while to update the position. This is because I live in an apartment block with lots of 2.4GHz RF flying about, so this helps to cope with that. I am integrating an accelerometer on the client to provide better intemediate updates when averaging is turned up too. But as you can see, it's pretty spot on in terms of accuracy.