I see Pete Stowe beat me to it with most of the details! I can't add anything further on Shepherd, whose demise was barely noticed by the Bath Chronicle in a short report of the meeting on page 9 of their issue dated July 12th 1955. Nor on Kasch - since the June 1993 microfilm is either missing or badly misfiled. 
However, Gordon Pill's death made the front page of the issue dated July 22nd 1963 and I can add the following: his full name was Gordon William Pill and he was 25 at the time of his death, which occured at the Royal United Hospital in the early hours of July 21st - the cause being stated as head injuries. The Chronicle adds the detail that his crash occured on a wet track.
His home was indeed in Oxford: his parents ran the White Horse pub in Broad Street and Gordon was employed as a clerk at Morris Motors. He had been a keen motorcyclist since childhood, had started racing in 1962, and was a close friend of journalist/bike racer Colin Fenton, who died in 2013: http://www.oxfordmai...ed_on_TT_track/