I'm in (long) training for my next appointment with an extension of service to 57; there is, all things being equal, a likelihood of being offered service to 60 at the same rank. I wrote to SPVA some time back when this was offered and, after many delays and making a Service Complaint, they eventually confirmed that my AFPS 75 remained unchanged (but also qualified it that they didn't know the impact of NEM - there's a thread running in parallel to this). Having said that I joined the RAF at 28 so I won't run too foul of the maximum years for pension accumulation.
I need to seek professional advice as soon as I am back in work; not having regular access to DII or JPA compounds the problem.