How about Tyro
Anybody on here spend a lot of time in MATZ? Is the callsign prefix TYRO still used? CAP413 "invites" students to prefix with Tyro when talking to mil radios and it's supposed to be in wide use in mil training schools. I have used it a few times when I used to squirrel around Middle Wallop in and out of Thruxton and it always worked.
Whatever phraseology is used, it can never be a bad thing to let the controller know that you're relatively inexperienced. "G-ABCD Student Pilot Solo" on first call for example.
Happy skies...