Sorry about not coming back on this point previously. Specifically, in answer to your query, the railway will not come searching for you at your employers. What you have done is dodged a train fare: unless it was for a much longer journey than I think, you have deprived the railway of a few pounds of income, and the worst that will happen will be that the courts charge you a fine (etc.) of some hundreds of pounds. That might seem like a lot, but putting people out to search for you would also cost hundreds of pounds. To be blunt, you're just not worth it - the railway will want to concentrate their limited resources against fare dodgers on people who cheat every day on their commute and should have paid thousands of pounds more in fares.
But more generally, I think (and this is rather tougher than what I suggested earlier in the thread) that the best advice is 'when you're in a hole, stop digging'. It's obviously worrying you that you gave false information and that this might have dreadful consequences. You can't at this point avoid the consequences of having given a false name - but you can stop the consequences getting worse by letting the railway know what your real name, address and age is. Write to them, telling them what your real details are (and of course telling them what the false details were as otherwise they'll never be able to tie the new information to what you originally told them). Since you are writing to them it would also be good to apologise for buying the wrong ticket, and explaining that you have learnt from your mistake and will not do it again - because that's what the railways want to happen: they don't want to keep chasing people for the right money, but for people to make sure that they have the right ticket at the right time without the railway having to force them.