Go
here to read all about it. But, in short the Royal Mail has issued a series of stamps today celebrating famous West End musicals. The Rocky Horror Show is one of these (along with Oliver, Blood Brothers, We WilL Rock You, Monty Python's Spamalot, Me and My Girl, Return To Forbidden Planet and Billy Elliot.
It's available from all good Post Offices now for only 97p. If you want one and can't get to a Post Office, then let myslef or Lucy know and we'll sort you out.