Also, not a 'brunch' in the 'traditional' sense, but head down for an early/late lazy lunch to The Boathouse in Stanley - very nice, quaint bar/restaurant that's been around for a long time now - it's a Stanley icon.
They do good seafood, but have a variety of other options to choose from - I suggest a whole load of seafood appetisers (get a platter, smoked salmon and bucket of mussels if you're going in a group) and then go for something lighter in the mains.
All this while overlooking Stanley - try to see if you can get a table at the top floor.
Will cost (depending on how much you eat and what you drink) between HK$200 - HK$500 per person.
Generally, 2-3 appetisers, 3 mains, 2 desserts, 1 coffee and a couple of glasses of wine sets us back about HK$1100-$1300 for 3 people.
Top Deck (Jumbo Floating Restaurant) is inexpensive with a great variety of food, but more for a group taking advantage of the freeflow drinks rather than looking for haute cuisine!
Zuma (Landmark) is a decent Japanese effort, great sashimi spread too.
The Mandarin Grill does brunch occasionally and it is excellent - usually on only on special occasions though (Mothers' Day etc)