Thanks everyone for your advice and suggestions, it was very helpful in reaching a decision.
I learnt that as things ramp up, I will need a few different tools, so no need to stress getting it perfect first go.
I checked out all of the suggestions (unfortunately our local Bunnings stores - 3 of them - don't have the Echo 2520) and bit the bullet today and went with Stihl:
FS70 Brushcutter
BG86 Blower
I still need to work out what to do about a hedger but figured I don't need to put all eggs in the one basket as I'll always need a spare whippy anyway (plus the blowers on those multi tools don't look super practical).
In terms of $s, I managed to come in on budget and get both for $760 ($410 for the trimmer and $350 for the blower - Retail is $830).
Spent a little more on the blower than I was planning and [I]may[I] have been sucked in by the anti-vibration feature of the BG86 instead of going for the BG56 or the Husq 125B...
Anyway, I think that's pretty good to get started... The trimmer in particular seems goldilocks as I don't think I have the skills for anything more powerful just yet
Again - thanks for the advice - it was all very helpful.