I dunno about that. The United States was six years of hard fighting with a couple years of kleinkrieg before and after. Malaya was twelve years of war that drew in troops from across the Commonwealth. Ireland was four-ish including the civil war that immediately followed, plus several decades of Troubles. Four years of Mau Mau fighting before Kenyan independence and another four after that British troops stayed involved for. Fifteen years in Zimbabwe/Southern Rhodesia, although the British themselves didn't fight in that. Several individual short wars in Palestine and Israel, plus a lot of low-level ongoing violence. The First Kashmir War in India ought to count. And there were a bunch of other situations that, while maybe not full-scale war, were messy and bloody in a way that probably would've been costly to solve more effectively. Britain's colonial projects didn't all end in total, unmitigated disaster for all involved like, say, Belgium's did, but that is not exactly a high bar.