Hi,
Welcome to RootsChat.
Have found an article in Kington Times 13 February 1959 where a Mr Natty Smith of the Caravan Site, Hoarwithy Road, Hereford was sold a caravan for £90. Unfortunately the man selling the caravan was buying it on hire purchase for £276, he got into difficulty paying the instalments and sold the caravan. He was unaware that he was not able to do so.
I presume this could be your grandfather (Natty Smith)?
JJ