Interesting thread. Having never used the service I don’t really have much to add (I really ought to contact them one day for a practice fix).
However with respect to the appropriate phraseology for a DF transmission I am sure that I heard somewhere that just transmitting carrier wave for a handful of seconds is better than saying anything as the carrier alone gives a better trace than a voice transmission (although it should be prefaced by “G ROTE transmitting for DF” or similar).
Can anyone confirm if this is true or not?