Bikes on trains in the UK

Two train journeys within the last few weeks, both of them on Southeastern trains.

1. Midweek ride back from Whitstable to London Victoria circa 4pm. No bike booking required but there were bike specific spaces on the mainly empty carriage. No extra cost, smooth as silk journey.
   
2. Midweek ride back from Canterbury to London Victoria on the 19:47 (even though I had pre-booked the 15:47). No bike booking required but no bike specific spaces on the train confirmed by the guard/ticket inspector I spoke to. I left the bike in the space by the doors leaning up against the non-driveside doors and all he asked was that I move the bike for the two stops where the platforms were on the opposite side (no-one got on at either stop).
   
   

For both of these I pre-booked the tickets a few days before and saved circa 50% on the cost if I had paid on the day (as evidenced by the riders I was with on the way back from Whitstable who ignored my suggestion to pre-book).