I've been entirely idiotic and would really appreciate any advice you can. I was caught a few months ago with a short-fared ticket and told that there would be an investigation. I have been buying short-fared tickets for a long time now, 2/3 days per week for a few years, and whilst I didn't admit that during the chat with the prosecuting officer, it is easily seen in my account. Quite frankly I'm terrified and would appreciate any advice that can be given. I haven't been able to sleep thinking about and just want to pay an out of court settlement on the amount I owe.
I discovered the letter today but unfortunately only have a few days to respond as it arrived a week ago. Any advice you can give would be greatly appreciated. Here's what I received:

I've been making the same journey ever since the incident and obviously pay full fare every time now. Is it worth me mentioning this on the letter? I am happy to make the full payment upfront if needed, is this something I should make clear in the letter also? Thanks in advance for any help you can give.
I discovered the letter today but unfortunately only have a few days to respond as it arrived a week ago. Any advice you can give would be greatly appreciated. Here's what I received:

I've been making the same journey ever since the incident and obviously pay full fare every time now. Is it worth me mentioning this on the letter? I am happy to make the full payment upfront if needed, is this something I should make clear in the letter also? Thanks in advance for any help you can give.