They are supposed to be very good! However, it is difficult to buy tickets out of the UK as they are a South African carrier with no real ticketing set up here!
Try getting hold of AVIANCE at Gatwick Airport - they are their handling agent and may be able to point you in the right direction of how to get hold of tickets!
The Gatwick Airport switchboard is 0870 000 2468 - ask to be put you through to the "AVIANCE TICKET DESK IN THE NORTH TERMINAL"
Good Luck!!!
Have a look at
http://www.flynationwide.co.za/ if you want info on this airline