The winner is....
My vote has to be for LHR T3, which has been a complete shambles for the past year. Catastophic landside, from being dropped by bus at arrivals for departures, flooded tunnel from central bus station, non-working travelators and escalators, security queues extended the entire upper departures landside, insanitary toilets, jam-packed departure lounges, insufficent seating, squalid food outlets, rip-off shops, slow baggage recovery, long queues for UK immigration and the mindless bureacracy that entails. BAA can't run the proverbial event in a brewery.
Luton by contrast is a sheer delight.