Exceptions are sometimes made, I flew in on the Flylolo/Flybe flight from Skiathos on October 2, and after being told shortly after a very late departure from Skiathos that we would be diverted to Exeter - towards the end of the flight we received the good news that SOU would remain open for our arrival, and touched down eventually around 23.40. But I think generally the restrictions are enforced fairly strictly as it is all part of the planning consent for airfield operations.