Holst Birthplace Museum, in Cheltenham, Gloucestershire. This is the Regency terrace house where Gustav Holst, composer of The Planets was born in 1874. The museum contains many of his personal belongings including his piano on which much of his music was composed.
Just for information, Fred & Rose West lived in a flat next door to Holst's Museum before moving to their infamous house in Cromwell Street, Gloucester.