Could someone just outline exactly what I need to do again if I want to download Pokemon from the Aus Eshop before doing the system transfer? I don't want to risk loosing anything but really fancy a shiny new game to play on my shiny new machine.
1. Get your new 3DS, set the country as Australia. DO NOT make an NNID nor transfer your UK account from your old 3DS yet
2. Go to the eShop and purchase OR/AS
3. Once finished, change country to UK
4. Transfer your account from your old 3DS. This will merge your accounts
Doing that you should be able to keep your UK NNID, all your games from your old system AND OR/AS from your new system
ONLY do these exact steps. If you transfer too early you cannot do it. Also bear in mind, that you may not be able to redownload OR/AS from the UK store before the 28th so make sure it doesn't get deleted during the transfer!