All four Zebra Finches that hatched earlier had fledged and seemed to be going well. During January, however, two died. Unfortunately I have no idea why.
The pair of Gouldian Finches in the main aviary have occupied a nesting box (after investigating all of the nesting boxes I installed) and are busy looking after a few eggs. In a week or so I should know how many have hatched.
I have started work on the construction of another, much larger aviary. It is based on an existing aviary I purchased off Gumtree (thanks for the help David!) that I plan to modify and extend with some large flyways and planted scrub areas.