Andy, with that TS80 triplet,which is a very nice, well colour corrected scope, you will need to factor in the purchase of the reducer corrector at some point (which gives you flat field and faster focal length), or you could just buy the flattener without reduction. If you go down to the bottom of that page you linked, you will see the choices of the Photoline 2 or 3" reducer correctors or just the TS Flat flattener. So budget for that. Or image at the native focal length to start out.
The post below is correct, if your total cost, including shipping, reaches $1000 Aud you will need to pay GST, which is collected inbound. So given the present exchange rate and shipping you will get hit with inbound charges.
There is a way you can get it under the $1k threshold.
Have a look at this TS80 FPL-53 Doublet APO:
https://www.teleskop-express.de/shop...n-focuser.html
It is a little cheaper than the triplet but still very capable for imaging. Native f7 it reduces to f5.5 with the reducer corrector. It is also a little lighter than the triplet version. Importantly you can get it shipped to you here for less than $1k, that is delivered, so no inbound charges (GST). Make sure you specify DHL delivery in the shipping options as that is much cheaper than UPS and keeps you under the threshold.
Once you get the scope, you can order the reducer corrector of your choice, and bring it in on a new order, it will be under the GST threshold of course. Don't bundle the orders.
Which ever way you go, i recommend the 3" Photoline Reducer Corrector, its very good, i have it. You could save abit with the 2" version if needed but it won't suit the larger APOs in that family of scopes.
Of your other options, i believe Option 3 is preferable. It is abit easier to collimate an f5 and it has less native coma, you could see if you can buy a second hand Baader MPCC, they do come up now and then on the classifieds.
Don't worry about Carbon Fibre at that size.
I should tell you that i just bought a TS80 FPL-53 Doublet APO and it arrived under $1000. I already had the reducer corrector because i own its bigger brother as well. Those TS FPL-53 APOs are excellent value and have very good rack and pinon focusers. Good luck