I'm scared thinking I may be locked up for this stupid act as I haven't had any criminal convictions before and had never done this before. I appreciate that you have quite a few queries on here but your advice is desperately needed.
Although it is technically possible to receive a custodial sentence, we can confidently say that you
won't get locked up. Only persistent, repeat offenders are at any risk of that.
The absolute worst that can happen to you will be a fine of £1000 (plus costs) and a criminal record that will appear on a standard DBS check for one year.
I truly don't believe you will get anything even close to that.
What will likely happen next is you will receive a letter from the train operating company (TOC). This letter will be your opportunity to try to convince the TOC that this case isn't worth taking to court. Your letter should show them four things:
1. That you understand that you should have bought a ticket that covered your full journey.
2. That you appreciate that short-faring costs them (and by extension all passengers) money.
3. That you are sorry that they have incurred additional costs in dealing with the matter.
4. That you will never do it again.
On receipt of your letter they will choose from four options:
1. Drop the matter with no further action taken.
2. Request an interview or further information before taking further action.
3. Agree to settle the matter for payment of the outstanding fare (with or without additional costs).
4. Determine that there are no mitigating factors and proceed with a prosecution
Seeing as it is a case involving short-faring on a season ticket, they are going to be interested in determining exactly how much money you have underpaid by, so I wouldn't be surprised if they go for option 2.
You don't need to instruct a solicitor yet, you may still be able to resolve this matter with a well-crafted letter. If this is not successful they might invite you for a friendly chat. If this happens, that would be the point to get legal representation. It doesn't have to be a railway specialist, any solicitor who is familiar with criminal law should be able to assist.