Thanks for the reply b789.
Quick update - I sent a complaint to the landowner asking them to contact NSGL to cancel the charge, but they have replied back to say that I need to follow the appears process on the letter to 'ensure that the appeals process can be correctly administered and governed'.
So it looks like I am going to have to appeal to NSGL instead.
Do I raise the point about the unclear signage at this stage or wait until I have a POPLA code?
Also, is there any mileage in me challenging back that I was parked in a marked bay, although one tyre was on the line?
Anything else I should consider in the appeal?
cheers