Re. Shorts Stirling.
From Wiki:
It seems the Air Ministry wasn't entirely clear what it wanted in the new design, and the resulting Specification B.12/36 was an odd mix of features. In addition to a 14,000 lb (6,350 kg) bombload carried to a range of 3,000 miles (4,800 km) (incredibly demanding for the era), the aircraft should also be able to be used as a troop transport for 24 soldiers. The idea was that it would fly troops to far corners of the British Empire, and then support them with bombing. To help with this task as well as ease production, it needed to be able to be broken down into parts for transport by train. Since it could be operating from limited "backcountry" airfields, it needed to lift off from a 500 ft (150 m) runway and able to clear 50 ft (15 m) trees at the end, a specification most small aircraft would have a problem with today. It is often said that the wingspan was limited to 100 ft (30m) so the aircraft would fit into existing hangars, but this is not the case. The wingspan limit was imposed in an attempt, unsuccessful in the case of the Stirling, to ensure that weights were kept down.
The idea that the wingspan restriction was because of hangar door sizes appears to be incorrect.