Musket old chap radicalist/fundamentalist/militant Islam declared "war" on the rest of the non-believing world about 43 years ago.

All instances where British Forces have been engaged on active service since the end of the Second World War have been in response to obligations related to bilateral self-defence treaties, in response to requests by the United Nations, in response to assistance requested as "Aid to the Civil Power", in response to obligations related to membership of NATO or in response to naked aggression and direct invasion of sovereign territory. IIRC 1968 was the only year since the end of the Second World War that no UK serviceman or woman was killed on active duty.

To state that the United Kingdom has not been "at War" since 1945 is not merely technically correct Musket - it is factually correct, perhaps you should review what it means for a nation to be at war actually involves.