qilich shared some research on Australian toy manufacturers, and reminded me of an essential source for research: the digitised Australian newspapers (1803-1954, but not yet complete) available on the website of the National Library of Australia. I have previously searched this, for family history and for dolls houses, but had forgotten about it when writing my last two posts.
qilich had found advertisements for the Marquis kitchen set in newspapers dating from 1948 and 1949, so they're earlier than I'd thought. The 1949 ad, which appeared in the Sydney Morning Herald on Wednesday 30 November, is wonderful, as it shows the whole set illustrated:

As you can see, it cost 22/6, which sounds quite expensive to me - although the year before, David Jones, an upmarket department store, had advertised it for 27/6!
qilich also found a 1948 ad for the Tiny Town Kitchen Set I showed in my previous post. It was on sale for 1/9; the original price was 3/7. Being on sale in March 1948 suggests that it was not new - I'd think it would have been released in 1947 at the latest.
The same sale included Miniature Furniture, 6/- now 3/-, and Morley Toy Furniture (8/6, now 6/-), as well as Little Housewife Sets (5/2, now 3/-). It might be possible to find out more about the Morley Toy Furniture, but (saving an illustrated ad), I doubt we'll ever know exactly what the Miniature Furniture was!
So, having been reminded of this wonderful Australian research source, I did a search for Wee Folks, the company that made the Dining Room Table and Four Chairs in my previous post. Turns out they were based in Melbourne - the company advertised in the Melbourne newspaper The Argus. The first ad I found was in 1944, for Skittles, The Old Favourite Game, 8/6 each. Other ads were for factory space, plastic moulding, staff (secretarial and packing), and residential properties to buy and rent. The company was also the subject of legal action in 1949, so the records of that case might give more information about the people involved. I haven't yet found any more information about their toys, but qilich also sent me a 1947 article from Australian Plastics about plastic toys, which shows the Wee Folks table and chairs:

The Wee Folks dining room table and four chairs are in the centre of this display from Australian Plastics September 1947.
So, there are ads for the 3 Australian-made boxed sets I've posted about which date from 1947, 1948 and 1949. All of them were available in the late 1940s, earlier than I had estimated in my earlier posts. Thank you, qilich, for providing evidence to date them - and for reminding me of a great resource for research!