It really is simple - each aircraft should have an ELT. All very clever but expensive and not practical if there are no electrics such as in a Tiger Moth or microlight.
If this is not practical etc then one person on board should have a PLB.
Note that an ELT is registered to and fitted to a specific aircraft.
A PLB is registered to a specific person and should (in theory) only be carried by that person.
In practice a microlight club will probably have a few registered to the club owner. The risk here is
that the club owner's wife will probably have a policemen at her door to tell her that her husband has been fatally splatted when he is sitting in the hangar wondering why the student is late returning.