Hi @dmcmacca and thanks for posting.
have you raised a dispute with TCP about this? Have you received the reference number for that? Can you post the first 3 letter of your online order reference?
See this post from a moderator regarding those sales letters.
"I'm really sorry but the order reference Z60 is not eligible for any offers. It shows that the order did not track correctly possibly due to there being multiple browsers open at the same time. Again, I'm sorry but in this case there's nothing we can do to help."
It looks like you are out of luck
You must have had a number of open windows on your web browser at the time, while you were comparing offers.