If you don't mind, I'm interested in hearing a little bit more about the trip you have planned. Very similar to you, I have been planning on going down the East coast of Africa, also from the UK down to Cape Town, and also at the end of December or beginning of January 2013, but instead by motorbike. So for all intents and purposes, pretty much your trip. But I have been a bit saddened that being on a bike means I can't easily visit safaris. So what I'm trying to say is I'm interested in hearing a bit more..
Unfortunately, as to your requests for passengers, I don't really check any of the boxes you asked for, as I'm not a doctor, mechanic, or chef. But I can cook, and would like to think that I have other useful skills.
A little about myself: I'm a 27 yr old Englishman, formerly an accountant in the USA, where I have lived for the last 15 years. I left my job for a more interesting existence. I'm a keen traveler (as is everyone here), enjoy sports, ..enjoy everything really, cheery and pleasant to be around, and I've been 3 months in Spain this year trying to improve my Spanish.
Anyway, just curious to hear more,
nottmrd @ gmail (dot) com