Branch Flying Pay
I haven't got details available at home, but IIRC, there are only 2 rates of flying pay for Branch Officers, I think I started on the lower rate and that I am now on the higher rate. As for Spec Aircrew, I qualify in 2008, i.e. after 8 years as Flt Lt, not 8 years after commissioning. The details are available the in AP3392(?) which can be downloaded from the intranet.
Although Spec Aircrew no longer exists, you will be in reserved rights to Spec Aircrew Terms of Service (SATOS). I reality this doesn't mean much for branch officers, your flying pay will stay the same, although you will receive a Spec Aircrew pension. Last time I looked (a year or two ago) it was worth £4k a year more than a "standard" Flt Lt.
You can apply to transfer to PAS 15 months or so before your SATOS qualification date, which should give you about another £9k a year on your pension, and another 5 years+ of pay rises.
Hope that helps
Daf