Just to get this straight, please correct any errors:
If you are promoted from Flt Lt to Sqn Ldr before age 35, then your 38 point becomes an option - so you have to give 12 months notice to exercise it? Promotees after 35 would have this option reset to give 3 years return as a Sqn Ldr.
If you are still a Flt Lt then you leave the service at your 38 point, as you would have to sign-on for further service. Offers of assimilation/PAS have to be accepted with 12 months to run to the 38 point. If you are offered further service (ie assimilation) surely it cannot be enforced without positive acceptance?