I bought my first scope (10in Skywatcher BD dob) from Andrews. Excellent price, quick service, no fuss. couldn't be happier with it.
I've also dealt with Bintel for various things and am currently in the process of buying a WO Megrez 90 and mount via 2 other companies. One an Adelaide local, and another in QLD.
I haven't completed the transactions for the Megrez and mount yet, but I am starting to find a common theme about buying scopes from AU dealers.
Generally speaking, they're quite good, and back their products. The simple fact is; they have to.
As a community, amateur astronomers are relatively closely knit. These companies are all supplying to a relatively small, specialty group. So if they don't do it well, word gets around, and the damage done to their business can be significant.
It keeps 'em honest.
That's not to say that every transaction with every dealer is guaranteed to be perfect. Even the most reliable can occasionally have a hiccup. There's also the occasional dud dealer. But that's true of any industry.
Keep in mind, no matter who you buy through, local or interstate, there is always a risk, no matter how small, that you might get the sticky end of the stick in the event something goes wahoonie shaped. It's the nature of the beast.
To answer your initial question;
I've not bought from telescope.com.au, so I can't comment on how good/bad they are.
If it were me, I'd go thru andrewscomm simply because I've dealt with them before and had a good experience. The best way to do it is to call them up and place the order.
I do recommend you make sure you know EXACTLY what you need (including accessories, mounts bits and pieces) before you start. It's not that the guys from andrews can't help you set up a scope from scratch,
it's just better that you know what you need, rather than them trying to fill in the gaps for you. That's how mistakes CAN happen.
Good luck.