Singapore Airlines
Flew from Manchester (UK) to Singapore with Singapore Airlines. The flight was suprisingly enjoyable. Plenty of entertainment options on the flight with on-demand audio and video. It was a day flight so didn't need to sleep, which is a good job because I can't sleep on airplanes. It was roughly 13 hours out (13.5 hours back).
I'm from Melbourne but have been holidaying on a few occassions (probably about 10) to Queensland (Brisbane, Gold Coast etc) and twice to Singapore (not just stopovers).
If you haven't been to Singapore before, I'd definitely consider Singapore Zoo (and Night Zoo) -- we had a great time there. Also, at Sea World, have you considered adding in either a swim with the dolphins or swim with the seals?
My wife has done both, and she and I swam with the dolphins last time we were there. Of course it's extra cost, and we booked well in advance. There was about 8 or 10 of us in the group, cost included a wetsuit, and time in the water with the dolphins, probably about 20 minutes or so from memory -- plus a lovely photo we now have on display at home!
For your day in Surfers, you might find Time Zone a little low key compared to, for example, a day at Dreamworld, Wet N Wild or Movie World. There are free buses to these theme parks all day from Surfers, we did that about 18 months ago (even spent time with a tiger at Dreamworld!). About 40 minutes by bus, and entry price is worth the entertainment inside. That's if theme parks are your thing!
If you're looking for shopping in Brisbane, the Direct Factory Outlets are a good way to go too -- lots of cheaper brandname stuff. I can't remember the exact address, was up there about 4 years ago (I'm from Melbourne). Look up that name or D.F.O. Brisbane. We have 2 DFO's now in Melbourne, the newest at Essendon Airport (near me) and the traffic daily is huge, lots of choice too.
Of course I have no relation to any of these businesses, just pointing out my thoughts!
For really big shopping malls, two of the biggest are in Melbourne, Chadstone and Highpoint both have around 400 shops. I would guess Carindale is probably the biggest in Brisbane, but not being a Brisbane Yahoo-er I couldn't be certain.
Will do one day!!