Do i require a visitors visa to South Africa,if i hold a united Kingdom of great Britain travel document.?

Iam a Zimbabwean in the United Kingdom and i hold a United Kingdom of great Britain and Northern Ireland travel documemt, under the July 28 1951 United Nations convention.

I believe the correct term for the document you hold is a "1951 convention travel document"

Since South Africa is a signatory to the 1951 convention, you may benefit from visa-free travel. The only correct answer will be given to you by the South African High Commission.
http://www.southafricahouse.com/
Tel: + 44 207 925 8901
Tel: + 44 207 925 8910
Mr J K Tiba, High Commissioner, tibak@foreign.gov.za

Even if you do not need a visa, the travel document will need to be valid 6 months past your travel dates.