From David Pitts answer above (and he should certainly know), you just need to "cheat" a little on the numbers.
Instead of saying 120 for pixel count (360 channels), set it for 160 pixel count to get the 480 channels you need.
That will get you the correct output.
The software driving it is now officially your problem.
The software is the easy bit

.
Good information, I was thrown by the fact that there isn't a RGBW profile already in the software (from what I could see from the manual).
I was wary of upscaling the number of Pixels as I would have thought that the software would still see the first 3 channels as the first pixel and not the first 4 meaning that you'd fall out of sync after the first pixel:
Pixel number: 1 1 1 2 2 2 3 3 3
Channel relates to in software: r g b r g b r g b
Chanel relates to on chip: r g b r g b r g b
However with a rgbw chip you run the risk of:
Pixel number: 1 1 1 1 2 2 2 2 3 3 3 3
Channel relates to in software: r g b r g b r g b r g b
Chanel relates to on chip: r g b w r g b wr g b w
Does this make sense?
If the solution to this is to literally just run the pixel length as 4 channels a pixel then its fine, but I was unsure as to if the firmware on the board played around with the straight artnet addressing of those pixels.
Has anyone got a working test of this or the ability to video a quick test for me?