Several years after the original query, I have finally uncovered leads and discovered my ggg grandmother is Janet KILGOUR.
I have the extract (17th August 1837) from the Parish Register of the Town Church on the Island of Saint Helena where Janet and Thomas AINSLIE were married on 1st June 1837 by W HELPS, Chaplain of the Troops. Witnesses were James KILGOUR and D MARSHALL.
The only other info I have to date is that their daughter, Martha Victoria AINSLIE was my gg grandmother, and married Edmund SHEPHERD (son of an 1820 Settler).
I would be pleased to hear of any information you may have gathered since posting your query in 2002!