In the end we did go with
African Photo Safari Kruger Park - Stu Porter - Wild4 Photography Tours & Safaris - South Africa and could not have been more pleased with the choice. Stuart Porter is an avid photographer, and you would be hard pressed not to get some great shots with his encouragement and willingness to spend the time to set things up for you. He has a converted Toyota jeep that is set up to cater for no more than three photographers that each have their own seat with access to both sides of the vehicle. Each shooting position has a support shelf for a bean bag, or Wembley mount which Stuart can supply to save you bringing one. I've attached a shot of us in the jeep below.
Stuart has a terrific knowledge of the animals and birds, not just their names, but also their habits. On several occasions he turned a simple animal sighting into the chance of a great photo by anticipating the re-appearance of the animal and positioning us there ready to take the follow up shot. The back shot of the Honey Badger is the one that most people would have got, the second one is thanks to Stuart.
I have uploaded my favorites to Picasa, so if anyone would like to take a look, drop me a note and I'll arrange to send you an invitation to view them.
If you are looking for a friendly, well organized, safari that is focused on letting you get the best shots that you can, then take a look at Wild 4. Just to make it clear, I have no financial or other interest in them, it is just that we had such a great time, and (I think) came away with such great pictures that I would like to put some independent testimonials out there for them, as that was one of the concerns that we had before we met them. Their web site looks great and has plenty of testimonials on it, but there wasn't anything independent on the web that I could find, and the truth is they more than live up to what you see on their site.