I've had occasion to take a good look at this aircraft (which incidentally is called the Supermarine Mk.26, they refuse to use the word Spitfire). It's a roughly 80% scaled down replica based upon the Spitfire Mk.25, single seat with electrically retracting gear and a 200hp horizontally opposed air-cooled 4-stroke engine.
It has not been certified in the UK, but has good potential to be. Almost certainly against JAR-VLA, through the PFA homebuilt permit to fly system. I understand that 3 kits have been ordered by people in the UK, one by ST Aviation - the UK Jabiru importer. ST are I believe hoping to certify it through the PFA but my intellegence sources don't tell me how far they've got. From my own investigations, I don't think there's much certification data available and the PFA's Chief Engineer is not going to nod it through, there isn't enough operating experience for that (and knowing him fairly well, he's somewhat risk adverse - as most people whose signature can allow a new aeroplane to fly tend to be !).
So, my gut feeling is that you'll see the first UK example flying under test conditions in a couple of years, and perhaps having full approval in a year or two after that. No doubt, in the time honoured tradition, it will need a fair amount of modification to meet the British interpretation of European safety requirements (that, in this case, is not a criticism of the British system, just a statement of opinion based upon my own experience of working on many such projects).
Why not ready-to-fly? For that it would have to be issued with an ICAO CofA, which means that Supermarine Australia would need a full manufacturing approval. I don't believe that they have the capability to do that without adding huge costs. I also suspect that if they looked at the economics of it, they would not consider that the extra cost of company approval, VLA certification, and product liability compensates from the additional profit of being able to sell the aircraft RTF when they already appear to be selling as many kits as they can build.
Personally, I think it looks wonderful and I'd love one. If I won the lottery tomorrow, giving up work, ordering a Mk.26 kit, and spending my time certifying it so that I could fly them in the UK is high on the list of things I'd think of doing with myself.
G