Places to look at in Hong Kong:
Uniqlo - of course.
Boggi - in TST, some seriously nice Italian style suits in some very interesting fabrics. If a Boggi suit fit you well, it would be worth considering going with them rather than PJ as they are fantastic quality and would likely work out a bit cheaper.
Take 5 - Best option for denim in HK - stocking Momotaro, Samurai, Iron Heart and the Flat Head. Good to just look around as its an interesting pokey store.
Armoury - good for a look but as others have said its very pricey.
Tassels - good for a look and potentially might have some good stuff on sale, stocks C&J, Edward Green, Alden.
H Houses Shop - this is a very weird small shop that I stumbled upon by accident. It appears to be selling shoes from Herring Shoes in the UK, so it carries some of their range. A few Alfred Sargents, Barkers, Cheaneys and Trickers but all in small sizes (less than 9UK).