Seems very strange that the manufacturer is stating it is not their manufacture.I can only assume that some form of upgrade was completed, possibly by a third party ie PCW in-store technician or the likes.
When PCW or the Dixon group purchase a block of machines, it is usually to a manufacturers specification and production methods. On this basis PCW/Dixon group can negotiate very favourable terms. All that batch of machines would be mass produced, and would all be of the same specification.There would not be a one-off in a batch.
I now how PCW work and their customer service methods may not receive the corvetted awards, but it would also depend much on the local management team, on how this matter is solved. What I would suggest is that you consult your local trading standards and have a word with them. They will give you all the help in dictating a correct styled letter. They could also involve the local Trading Standards within the area of the DSG groups main headquarters, who no doubt have a regular contact point.
I know how these thing can get you angry and very uptight, but I can only wish you luck, hoping that the matter will be solved very shortly.