It is thought that this is the 'punchline' to a poem of John Betjeman. the story is of a Home Counties gal who goes up to London, to Art School? lives a nice bohemian life, then goes home and marries a local lad. the poet comments 'they always revert to type' it does SOUND like a Betjemanesque line, story and all, but where?
Ian - in Pheme's link, the end of the paragraph headed Critical perspective is a quote more or less the same as revcaroline's post. However, the quote's source poem isn't given, more's the pity.