I am guessing but a reason to maintain flights to and from London is to take Thai students back to Thailand and if correct in my opinion that's a good enough reason. A friend of ours has bought 3 tickets so far for her son to return to Bangkok, but all wasted due to having to comply with the new requirements.
If anyone has any experience of travelling back to Thailand and complying with requirements in OP then I would appreciate knowing as I would like to return home to Thailand