We stayed during the fringe, and had a wonderful stay. The flat was in a great location for us and we found everywhere we needed to be within a 30 minute walk.
The check in and check out was easy with the locked box once we found it, thanks to Tom's pictures. The only things I would change are having a door on the second bedroom and the price point, but I guess it's to be expected during the festival. Overall really happy with our stay and would recommend.