The only helicopter loss that I can find in my records that seems to come close to the circumstances that you described is as foollows.
27.01.75 XR454 Whirlwind HAR10 of 84 Sqn. Written off after foreign object ingestion caused the engine to fail. The tail boom was severed in a the heavy forced landing on Mount Troodos, Cyprus causing damage initially assessed as Cat 4 but later recat 5.
I would also be intetrested to hear if anyone has any additional details on this incident.