I did the 2R71 service that leaves London Paddington at 18:58 bound for Reading, getting there with the same train you collect it to the garage, but the passengers do not leave the train. Please correct this, I think it should happen in all services where we have to collect.
GWE passengers love the depot. They will happily stay on the train while you park it up and lock the shed for the night. In the morning you can pick them up again and bring them back into Paddington or Reading. I imagine they have a pretty comfortable night of it. And it's an economical way to spend a night in London, if you've seen AirBNB prices lately.