I have taken a photo of the filling station and also have a contemporary photo from around 1930. In those days it was called Brunskill’s Shell Garage and had a rather striking, period, five-sided pagoda style slate roof, the style of which is preserved to this day. It is located on the main A40 (London Road), quite near the centre of Cheltenham, and was the town’s first petrol station. I will submit the photos if someone can tell me how.
The information source was a lady who contacted my historian friend within the last couple of years. Apparently, a close relative of hers (grandfather possibly) owned the garage and had told her of Jerome’s visit on the day of his last journey from Devon.