Train cleaning

I wandered if there is a place to apply to clean trains inside or out? 14 years ago, somebody took me to the Clapham junction depot. I thought it sounded like a good out door job. I also heard a few Portuguese speakers and I wanted to speak my mother's language with someone. The kind recruiter told me he wouldn't hire me as somebody as young as me should try for university. So I did, but it didn't work out as well as it could have. I have ended up doing outdoor work almost ever since. When my child was born, I became a dustman. Night work is now my ideal however and I remembered the appeal and teamwork of the job. I tried to look for the depot entrance from memory and cnot find where. Or where to online? Is that line of work still available to directly apply to or must one go through agencies? Is it only Clapham Junction? Thank you for having a look at my query.