Left luggage at HK is in the central part of the Arrivals Hall. It works fine.

An alternative way to spend your time would be to take a taxi to Tung Chung (it costs about US$3), and then take the new Nong Ping cable car up to see the big Buddha high up on a Lantau hillside. The cable car ride is good and the Buddha worth seeing. The shopping centre at Tung Chung is an outlet centre, so good for an hour or so (though the shops are not fully opened yet), and there are some reasonable places to eat.

From Tung Chung you can take the subway into Central - it takes about 25 mins and is much cheaper than the Airport Express.

If you are really desperate you could always go to Disneyland I suppose (but personally I would rather have my finger nails pulled out).