I've just been lent a lovely *cough* Besson Sovereign trombone with F attachment that must be on the upside of 15 years old. Problem is, I've only been playing a peashooter up til now and this whole trigger thing has got me a tad confused. Are there any good 'get to grips with the F attachement' type excercise books out there?

I suggest that you start by playing chromatic scales downward from the notes that you get with the trigger and first position. If you have an electronic tuner, set it to listen to you and watch it. You will find that the slide positions you want are longer than the ones for the corresponding intervals on the Bb basis. If my calculation is right, 7th position on the Bb tenor is slightly short of what you want, combined with the trigger, for the notes of the C harmonic series.