Thanks to all of you for your input.
At the time of purchasing the ticket I stated that it was a Bank Holiday and the seller unsure turned to his colleague who had to confirm that fact to him.
He then stated that "Only during July and August" can you use the YP before 10am on weekdays for fares under the threshold - eh what about Bank Holidays.
As someone correctly identified I spent money on a First Class Stamp to send my letter to East Coast in Plymouth. The reason I had to do this was due to an error on their part.
When I eventually receive my recompence (up to 14 days) I will still be down the cost of the stamp.
I would have knocked out a letter of apology with permission on it to use the First Class Lounge at Edinburgh on it's production on one occasion. Bang problem sorted. I would have been quite happy with this - I don't expect a free First Class ticket to anywhere in the UK.