Just to be contradictory, my Gt Gt Grandfather was also an engine driver for the London Brighton line, working his way up from engine cleaner. I doubt he even went to school let alone a grammar school.
I've been fortunate enough to have seen the railway records held at the National Archives, and if you are lucky enough to find your relative in the employee records there is quite a bit of information so well worth the trip if you can. Sadly I didn't find my relative, but there was one volume of employee records that has not been released yet, so here's hoping.
Cheers
Caz