@Paul, did you run the Johnson Crane marathon? Many people use this race to qualify, but it is a relentless race in that you have to exert effort all the way, because it is so flat. It is also usually quite hot at the end of January.
Pick n Pay is not a very easy race to run also. As Madelein says, it is quite undulating and the finish can be quite excruciating, especially if you are struggling to finish within cutoff.
The easier qualifying race may be Township marathon, at the end of February. It is usually on the last Sunday of Feb, so most people are well into their training and are mentally and physically fit to run a marathon by then. It is a level 2 race (as opposed to the level 5/5 Deloitte marathon the day before in Pretoria), so not quite as flat as Johnson Crane, but a little easier on the body and mind.
Good luck!