The ELT does not have to be registered to an aircraft, it can be registered to a dustbin for all the MCA care as long as the know who to contact if it goes off. A flying club would buy them and register them to the club. When you file the flight plan you put the EPIRB Hex ID onto the flight plan at the bottom. If the ELT is activated they contact the registered holder and the holder will then confirm via the booking out system log if the flight is real or it is a false alarm.
The average location time in Europe for a GPS transmitting EPIRB is 12 minutes not 90. A multi frequency unit improves the rescue rate to an average of 30 minutes from activation.