Just on the subject of Gatwick and the Beehive, it's possible to buy parking at the Beehive for £5 a day via yourparkingspace, (referrals available via DM for a free fiver credit I think) with about a 20 minute walk to the modern terminals. For anyone with an interest in civil aviation history it's ineffably cool to park outside the Beehive, which still has the rails on which the early airbridges extended out to the aircraft. It's now bookable office spaces.
We're quite well served for early airports in the UK SE. Most of the Croydon terminal is still there and worth a visit for the museum and tower, and the lovely Shoreham art deco terminal is still used for general aviation.