The British Tar, a British barque of 282 tons (some sources give 309 t), built 1845 Sunderland, was wrecked on the "Back Beach" (i.e. Addington Beach), Durban 29 Sept 1850 in a gale. No lives were lost. Sources: Cape Town Mail 19 Oct 1850 Lloyds REgister 1850-51 Shipping Register, Cape Archives C.C.2/17
Information from "Shipwrecks & Salvage in South Africa" by Malcolm Turner pub C Struik Cape Town 1988
102 persons on board, mostly W J Irons's Wesleyans.
More detail and passenger list in John Clark's book "Natal Settler-Agent" as you probably know.
"Lantern" magazine March 1974 Vol XXIII No 3, specially produced for the 150th anniversary celebrations in Natal, carries several background articles on the period you mention, and includes some good illustrations. Should you have difficulty accessing this journal let me know.