The railway pensions scheme is final salary. It might be an umbrella that all the TOCs come under, but should all be final salary.
Sort of. I don't know whether any sections of the RPS are still 'true' final salary, but many were changed five years or so back to raise the age of retirement from 60 to 62 and to impose a limit on how much your pensionable pay could rise by each year, and introduce the concept of restructuring premiums which are increases which only count towards your pension from the time they came into effect, not from the start of service.
With the important caveat that I am not qualified to provide financial advice and you are encouraged to seek the assistance of a professional financial advisor:
For instance (note: simplification not taking into account inflation), if a cleaner started on £20,000 for ten years, and then became a Driver on £60,000 for ten years before retiring, it would not be calculated as (20 years service / 60)*£60,000 = £20k/annum, it would be calculated as (20 years / 60)*£20,000 + (10 years / 60) * £40,000 = £6.6k/annum + £6.6k/annum = £13.2k/annum.
If you served 10 years as a Driver before retiring - assuming GWR use the same system as above used in other TOC RPS sections, then your likely pension income would be:
The salary you started on, increased by RPI+0.25 each year * (10/60)
Plus, each time you received a pay increase, the value of that pay increase from the day it was counted as pensionable earnings * (years since that happened/60).