I just wanted to share my experience at the All Stars Inn on Beale St. It's one of the hotels you can select for the Southern Explorer as a start and finish point.
I booked in an extra night which was fine. At check out the next day I spoke to reception staff and they helped me book a shuttle for that night and helped me store my bags so I could go explore for one last day. The shuttle was booked for 3am and I arrived back to the hotel to wait at 1am. I asked the night manager to open the luggage room, at which point he rudely interrogated me about who I was and when I had stayed and why my things were stored. He then told me I couldn't wait in the lobby and needed to leave the premises. It was 1am, raining and the middle of winter. Luckily I was waiting with another topdeck traveller and we were able to arrange our shuttle to pick us up earlier.
If it was against policy that would be fine. However considering I checked that it would be ok at the start of the day, and saw others from my tour wait for pick up the night before (without even having ever had a booking) it was really upsetting to be thrown out into the street in the middle of the night in a foreign city.
The other hotel used is Break Free on Cashel. They were great when I stayed at the beginning of my trip and they're in a better location to see Christchurch by foot. If you choose to stay at All Stars, careful your flight is close to check out time or else you could be out in the cold too.