Emily - My in 2012 was run 9km and walk 3 minutes off a 3:20 qualifier. This worked pretty welll for the first half and then my runs and breaks got shorter. The important thing is to start the walking from the beginning because when you are tired it is too late.
If you listen to Marathon Talk, then listen to the interview from Prof Tim Noakes for the principles.
I can remember where I got my specific advice from about the run 9km and walk 3 min. If I can remember correctly, then with your qualifying time you should walk more frequently. I'll try and remember where I got if from and let you know.
I worked in miles for Comrade and just used my Garmin. It was my first ultra so large number like 56mile 89km were meaningless anyway. Anyway, most of the km marker signs had blown down.
I'm registered to run for England, not the UK. My wife is from Potchefstroom ion SA so my in-laws are very impressed as I am the first family member to run Comrades. I will wear my Union Jack shirt as it got a lot of support last year.