Hi. We went through a similar scenario awaiting the SA Police Clearance Certificate. We used a courier agency recommended by the SA High Commission here in London. It cost ?140.00 and took 7 weeks but we received the correct form in the end.
Try
yolies@netactive.co.za or Yolande Pienaar, DKP Investigations CC
Tel: +27 11 8153962/3 and Fax: +27 86 689 5078
These are the details of the company that helped us out. Their London contact was a bit useless but came through in the end.
Our ITA was received by NZ Immigration in London on 8th August and we received the wonderful "Approved in Principle" on 13th August.
Good luck