Nowhere else in Europe insists on the Hectopascal read back and American crews fly to Europe.
The auto frequency change is not difficult. Some of the largest airports in Europe use it very effectively to cut out unnecessary chat.
Just saying that a lot of the problems you mention are not directly under Luton's control but rest with the CAA and NATS so won't be sorted quickly and can't be sorted by the airport. .
The London TMA is more complex than most in Europe with many stakeholders and lots of traffic. Witnessed it yesterday in My Jodel joining the circuit at White Waltham with an A380 2000 feet above me on left base for LHR