No doubt the greatest moment of the Royal Navy in living memory was the Falklands conflict - which had nothing to do with a "threat to NATO".
Since 1982, rightly or wrongly, the British Army has committed significant number of troops to combat operations in Kuwait, Iraq and Afghanistan. Again not NATO operations.
British armed forces have historically, again one can argue rightly or wrongly, been repeatedly committed to operations that have little or nothing to do with NATO. They are an instrument of Britain foreign policy, and provide the politicians with options.
While a debate of the various size of Navy, Army, Airforce assets in a limited funding scenario is valid, this being pprunemil, I can alas see such a discussion rapidly descending into a p***ing contest where people argue for their "favoured" service.
And no, I 'm not ex Army.