Danny boy! You want us to hand over all our proj's and then pay you to teach us to climb, bit cheeky lad!!
Namibia is reportedly not so good on the bouldering front, and is f-ing far from the Western Cape. About a day and a half's drive, South Africa is also quite a big and very spread out place. Best place for hard sport climbing is in Oudtshoorn, our only limestone crag, which is about five hours from Cape Town roughly in the center of the country. Routes up to 8c but only one undone project which is probably about 7c+. Also hard sport in Montagu 2 hours outside Cape Town (en route to Oudtshoorn). Several proj's there but as they are somewhat coveted you may have to beg to be shown them, kidding - buy 'Western Cape Rock' the local sport gudebook, for bouldering topos you'll have to trawl through the websites and look for dl's - check links on this site.
Dont know about car hire, but there are numerous smaller companies in CT which may not rip you as much as the bigboys, check it once here. Contact City Rock Gym (gyms are always a good port of call in a new city - cityrock.co.za) re the training thing, might be some interest. SA climbers are super friendly, provided you leave the attitude at home!
Have a great trip!