Beware of hidden costs when shipping vehicles
We read about companies having hidden costs that you do not realise until too late.  It is true.  When we booked the shipping we checked in the UK that all costs were included - and we thought they were.  When collecting the vehicle we found out that all costs after the ship docks still had to be paid before the vehicle can be released.  This cost us an extra £600.  So, make doubly sure when you ship the vehicle you know that all charges are covered and that you have enough extra cash  - just in case!
(Additional Note:  The overall cost of shipping the car was around £2000 all in, and was very easy/quick and safe to do, so apart from being aware of hidden costs, it was a good idea.)

Check you've actually got all the keys you need to unlock all the locks on the car
It's in the diary.... enough said!

Everything is actually more expensive than you might expect
Camping in proper campsites is actually quite expensive as you pay per person rather than just for 1 tent.  In SA we are paying on average 100 Rand per night (~£10)

Road maps are not that accurate for smaller roads
Better to rely on asking the locals (and it helps you to learn a bit of the local language and pronunciation!).

Buy a decent shovel
We did and it saved us twice (so far).
(And a smaller, easy to get to, one is useful for toilet stops!)

Keep any spares you want to keep hidden
It is difficult to not give/sell your spares to the local who really needs it when it is out on show for him to see.

Before you leave check everything on car can be undone
It's annoying when you find out a bolt/screw is rusted on and can't be done when you are away from home with limited tools and time.

To take mountain bikes or not?
Originally we thought taking bikes would be a great idea, and on the few occasions we use them, they are a great idea.  You can leave the car set up and cycle off to explore cities/villages/game parks etc.  BUT, they are the most obvious thing on the car, everyone stares at them and asks for them, you feel very self conscious with bikes on the roof.  At times they are a hassle when pushing through low bush.  We haven't used them as much as we thought we might.  In hindsight we would not have brought them, but they have been useful.  If you are thinking about it, I'll leave you up to decide for yourself...

Fear is worse than reality
There are various countries we travelled through where we were very nervous based on reading guidebooks.  In reality we have found everyone to be very nice and friendly and as long as you remember to smile and stay relaxed it is all fine.