I have had an email notification saying my flight to Ibiza next summer from LCY will be operated by Stobart Air and that they are allowing me to change onto any other London service to Ibiza within 3 days. My MMB still indicates the flight is operated by BA Cityflyer on an Embraer E190SR. I guess I will wait and see what happens, either way - I don't want to be rebooked as the current flight time is perfect for me. Just checked a new booking and there is no indication that Stobart Air will operate the flight, so the email could have been sent in error.