There are plenty of good tips for a HK stopover on the Destinations-Asia-HK section on this forum:

http://www.flyertalk.com/forum/hong-kong-macau-436/

Don't bother going up to Victoria Peak if it's not a clear day/evening as the views are dramatically reduced. At the moment, the pollution in HK is so bad that we can barely see Kowloon from HK Island. Pollution is literally off the WHO's danger scale. But last week was sunny and clear so fingers crossed that you get lucky.

If you decide to eat "in town", I'd suggest you go to Soho (just up the escalator so 10 mins from HK Airport Express station at IFC) as there are lots and lots of restaurants (and bars) covering all budgets and cuisines.

I definitely agree with everyone that you should get the Star Ferry. Try and be either on the ferry or on Kowloon harbourside at 8pm for the lightshow. It lasts around 20 mins I think. Note that you can also get back to HKIA from Kowloon Airport Express station so you don't need to go back to Central to get the train back if you're Kowloon side around 9-9.30pm.

As a Brit, it may be interesting for you to know that one of the few things cheaper in HK than UK are Apple products. There's no sales tax in HK so Apple prices are pretty much UK price minus the 20% VAT. There's an Apple store in IFC (above HK Airport Express station). A lot of my European visitors make a trip to the Apple store here lol.