I have claimed twice for the refund of nugatory holiday expenses after agreed (and signed off) leave had been cancelled due ops.
First time I had no insurance in place (Kosovo), second time I had insurance (GW2) but company would not pay up.
Received a full refund on both occasions.
There is a link here to it being discussed more recently.
Holiday Cancellation [Archive] - E-Goat :: The Totally Unofficial Royal Air Force Rumour Network forums