Anne Marie and the Pale Pink Frock. An illustrated children's novel of the Great Trek in South Africa.
The Citadel is Yours. Contrary to the title, it has nothing to do with Cloister and the Citadel and is a modern medical novel.
The Covenant. "The adventures of a South African family of British descent during the Boer War and afterwards." (from a review in Time and Tide)
Dark Star. A historical novel set in 17th-century England.
The House of the Seagull and The House of the Swan. I know nothing about them other than the setting: the Netherlands in the 16th and 17th centuries, respectively. There seems to be a third novel, The House of the Bird of Paradise, though it's not listed in the bibliography I own.
Not by Any Single Man. A novel set on the coast of Kent during the French Revolution and Napoleonic Wars. A review in The Observer compared it to the best of Du Maurier.
Old Amsterdam. A sequel to I Struggle and I Rise, it follows the fortunes of the Van Breda family in the 17th century, particularly one of Anna's grandsons, Pieter, a Dutch financier who falls in love with a distant relation. It has a lovely old-timey cover, pictured at above left.
Westward the Sun. Novel set in South Africa at the turn of the 20th century; it may be a sequel to The Sun Climbs Slowly.