Those of you who know Horfield will remember that the usual offices were at road level, and there was a longish walkway down to the footbridge. Now, alongside this walkway was a very appealing grassy bank which was rather nice to sit on if we could get past the stationmaster - which we sometimes did.
Unfortunately, one of them was extremely bad-tempered, and having received his boot up my backside I decided not to risk it again.
Were others banned from platforms? Certainly, in my many railway books there are plenty of photos with spotters happily sitting on the platforms in various Western Region locations.