One wing of the Coatham Hotel was never completed in the style of the rest of the building and the Windsor Ballroom was added some time between 1955 and 1961 (see discussion in comments). In later years it became a nightclub and a gym.
The lop-sided appearence of the hotel made it perfect to be a bombed out Dunkirk ruin when Atonement was filmed in Redcar in 2006
The building has remained derelict since with its French set-decorations still on display, until August 2011 when its been given a fresh coat of paint and is now covered.