Hunter GT6 - very spurious!!, surely a stripped down single seat F6 with no sabrinas dosnt qualify as a trainer!!??
How about Typhoon T1 (T1 - come on really , how can a trainer come before the fighter variant!!??) or Tornado F2/3(T) or Tornado GR1(T), Harrier T10, Jaguar T4, Lightning T4.. depends how you define "trainer"
I think the Athena T2 did enter service but more of a glider tug than trainer.