I'm kinda glad it wasn't just me...
Did I mention that I destroyed and recreated the array in the RAID controllers BIOS also?!
So, I just got a reply from Highpoint, turns out their RAID management software doesn't work with 8.1, only upto 8.0
They said to wait a few months! lol
From what I can tell, that means that the array is not able to be initialised, hence not actually built completely.
I have created a JBOD array instead, and will see how that turns out.
Thanks again for your time, I'll let you know how the JBOD turns out.