Another famous UK one is the Beaulieu Dairy House and I'm sure I heard of urban ones disguised as news stands and small shops and of at least one other rural one disguised as a garage.
Yes - there was a book about wartime preparations in Acton that mentioned a 'coal merchant' pillbox on Brunel rd. and others disguised as news or ice cream kiosks. It also mentions one that had the roof of a Police call box on the roof - presumably to make it look like protection for the box rather than an emplacement.