Actually, I'll take this opportunity to point out that I am happy to proof read in cases where the passenger is in the right, and/or has been harshly done by, and is appealing against some wrongdoing. I've had a lot of success with that sort of letter, but this case is very different.
In cases where the passenger has actually done wrong but is fully co-operating and genuinely sorry etc, I may be in a position to help, depending on how busy I am.. but I am not in any way 'qualified' to help with those sort of cases. I'd suggest contacting a solicitor (which I most certainly am not!)
But when questions I have asked have gone unanswered, then I am not in a position to be able to help. Specifically I'd like to know when & where the ticket was bought, the price of the ticket, whether or not the ticket can be found (and if not I'd like more information as to why not), and when the next journey to Manchester was made, however the OP is under absolutely no obligation to answer these questions. But, I suggest, if these questions are not answered, that the defence/excuse of having left the ticket at home, is perhaps best not used. I also suggest finding someone else to proof read. Sorry if that sounds harsh.
Edit: I suggest the OP contacts a very good solicitor, that's all I can say on this subject.