Low n slow on the subject of ELT ,s in G aircraft i think that one can be fitted but it must have a warning in the cockpit to show when it is transmiting ,most light aircraft ELT,s dont have this function.
I am at the moment looking into the ameri-king AK-450 as the glossy flyer seems to say that it has the indications that the UK CAA require but untill i get my hands on a wire diagram i wont know for sure.
The unit is atractivly priced at about $270 for a G aircraft and it meets TSO-C91a.