AFAIA it is based on the gross salary per your P60. This includes Profit Share if taken in cash, Notional pay, BIK etc but excludes Tax Saver travel scheme.
Your final salary for max pension allowed by revenue is also based on your p60 so you need to be aware on this when coming to retirement. won't happen for at least 25 years in your case i.e. in final year don't use the travel save scheme.