Thank you for your reply Steve, I put in some DPF cleaner yesterday and then some fuel (not a full tank) and within minutes it had started doing a regen. Not sure if it was just a coincidence but I kept it running until it finished and these were the numbers.
Measured = -6.24g
Calculated = 5.26g
Oil ash mass = 34.46...
I then cleared the code and so far this morning it hasn't come back on but if it does I'll get in touch with the company and leave the code there.
Thanks, Jordan