Some Castleton history (pdf) by Peter Harrison says (although this presumably isn't 100% accurate):
Over the road and opposite the school is a wooden single-storey shed attached to a well-built, dressed limestone, two storied building. It was built as a Primitive Methodist Chapel. The Methodists moved elsewhere and the Chapel was sold to George Boam and Sons. They established a mineral water factory in the Chapel so it became known as “The Pop Shop”. Eventually the Boam’s sold out to the Ackroyd brothers (John and Henry) who continued the business until the mineral water business closed completely.
The Pop Shop, as it had by then become known, was used by the Kelsey’s, (Drury and his son John) as a furniture store. Their furniture shop was in Swiss House on How Lane. When Kelsey’s moved their storage facilities from the Pop Shop to the Peak Pavilion the Pop Shop was sold to The British Speleological Association. (B.S.A.) and it became their headquarters. In 1974 The B.S.A. merged with The Cave Research Group. (C.R.G.) All their records etc. are now stored in the Pop Shop. It is still the headquarters of Cavers, Cave Divers and Pot-holers and the Society is now The Technical Speleological Group. (T.S.G.)
