You don't say what sort of passport you hold, but assuming you don't need a visa - then go through immigration as fast as you can (it is as long a walk as from far gates as at Hong Kong - but without the train) and get the UAE stamp in your passport.

You can then check in fairly quickly and head back into the terminal proper for duty free - including the infamous win a car draws.

The airport is busy virtually all hours, and there is no fastrack security lines other than for Emirates passengers, so the departing passport and security check can take upto 20 mins for the BA flights I have done in the past. The BA Lounge is nothing special - the terminal is much more interesting !