Private parking company fraud?

[deemin75]

On July 5^th 2019 my car was parked in a privately owned parking bay near Brighton seafront. The company GXS Services Ltd issued me with a parking charge notice, and despite having tried to appeal to them (on 09/09/2019 and 22/10/2019), they gave no acknowledgement of ever having received my initial response and continued to send me letters insisting that I pay for the parking charge in full, now amounting to £160.00 as of 20/01/2020, under threat of escalating the matter to a level whereby court proceedings are initiated. I highlighted in my second letter to them that there was no photographic evidence of a parking charge notice for this offence, to which I received a response from them on 25/10/2019. I have now received, on separate occasions, two photos - the first of which (22/08/2019 - in the original letter) depicted my car parked on private land, and the second (25/10/2019) showing this exact same photo only now with a visible parking charge notice that has been photoshopped to appear affixed onto the windscreen of the car.
This is a clear fabrication given how every single aspect of both photos is identical apart from the yellow parking charge notice seen on the windscreen of the car in the photo illustrated on their letter to me dated 25/10/2019. It has now reached the stage that I have been sent a letter from Trace Debt Recovery UK Limited (a company for which GXS Services Ltd are clientele) continuing to demand payment under further threats of taking the case to court, and as such I would like to request from you some advice on how to proceed with dealing with this situation.Any thoughts?