You may laugh (although only if you've been through it :-) but I nominate Norwich Airport
Pretty standard shed structure, cheap finish inside and no real excitement or thought in the design, BUT the management have not succumbed to the blatant commercialism of modern airports (for an excellent critique of airports becoming shopping malls, see the Harvard Design School Guide to Shopping
). As a proudly minor league regional airport with only a few flights a day, it has a charm that is rarely found, and a cafÃ© that is open to the public in the check-in hall that overlooks the aircraft stands. Whenever I pass through, people have dropped by for a coffee, a fry-up or just to watch the planes go by. You can actually see through from the front to the back, an original dream of Foster for Stansted, now shamefully lost by the rampant commercialism of the British Airport Authority, who have ruined the clean, uncluttered interior by filling the airside with a slalom of shops and restaurants to suck every penny from the supposedly low-cost traveller.
Perhaps the low-cost airlines could be exploited to build a day's architectural tour of airports around the UK? It would be very damaging to the environment, but since the planes are going to be flying anyway, we may as well make the most of them... any suggestions?