Welcone to the forum!
Did you really think you could only use a ticket once, or were you chancing it and hoping you could get away with it?
As for what will happen next I expect you will receive a letter from the train company or an investigation company acting on their behalf. The letter will typically take a couple of months to arrive but can be sooner although it shouldn't take longer than six months. The letter will say that they have received a report, are considering prosecuting you and ask for your version of events before deciding how to proceed. It is important that you engage with and reply to this letter. You might want to include the following in your reply:
- That you are sorry for what has happened
- What you have learned from the incident
- That you are keen to settle the matter without the need for court action
- Offer to pay the outstanding fare and the train company's administrative costs in dealing with the matter
Make sure your reply is short and concise, don't give a sob story - they've heard it all before. Most train companies are usually prepared to offer an administrative settlement (commonly known as an out of court settlement) for people who engage with the process and who haven't come to their attention before. There is no guarantee of this and the train company would be within their rights to prosecute you in the magistrates court.
If you are offered a settlement the amount varies depending on the train company and circumstances but tend to be a few hundred pounds plus the outstanding fare. An out of court settlement might appear to be a fine, but it isn't and you won't have a criminal record as a result of accepting one.
Feel free to post a copy of the letter once it arrives (with personal details redacted) along with your draft reply in this thread and forum members will be happy to proof read it. for you.
One further thing is that as you're in student accommodation is to make sure you have access to your mail when you are away, for example over the Christmas holidays.