Don't Panic Chaps! (1959)

Sent to a lonely island in the Adriatic to set up an observation post, four British soldiers realise they have been forgotten when the scheduled submarine fails to show. They are not alone however. A small German unit, also marooned, is comfortably ensconced on the other side of the island, well stocked with provisions. Both sides decide nothing is to be gained by continuing hostilities and the British move in with their well-maintained enemies to relax for the duration. All is harmonious until a glamorous castaway arrives on a raft. From then on battle is resumed....and it's total war!