I grew Geranium x oxonianum 'Walter's Gift' from seed from the UK Royal Horticultural Society and it is one of the few true Geranium plants that I have been able to retain in my garden. It has attractively burgundy-marked leaves and netted pale mauve flowers in September and October. I am not sure if my version is the same as the true cultivar - because of the variation that can occur with named plants like these grown from seed, but I nurture it as one of my plant 'children'. It grows into a clump (ht 20 cm) and self-sows freely, and usually other gardeners are pleased to take one of the seedlings home. It prefers full sun and reasonable soil but can also tolerate some shade (but not heavy shade) and a degree of dryness. Cut back hard after flowering for a flush of new leaves.
Geranium x oxonianum is said to be a cross between Geranium endressii and Geranium versicolor. Another cultivar of this Geranium is 'Claridge Druce', which has bright pink flowers with dark veins, and can also do quite well in Sydney.