This is inaccurate, I'm afraid. Michael Collins was not executed by the British
during Ireland's war of independence, but was ambushed and assassinated by the extreme Nationalist wing which refused to accept the agreement he had negotiated with the British for an Irish Free State inside the British Empire.
His killing was therefore the result of an internal Irish Civil War, not anti-insurgency operations of the ocupying power.

To this day, there is controversy about what actually happened at Beal na Mblath (besides the fact that Michael Collins was ambushed and killed), However, there is no controversy as to the fact that the British army assasinated Avraham Shtern.

Again some confusion, I'm afraid. It was Etzel commander David Razi'el who was killed in Iraq, whence he had gone on a secret mission for the British Army during the Rashid Ali revolt of 1941. If I am not mistaken, his car was strafed near the British Air Force base in Habbaniyya.
Etzel had declared a cease-fire after the outbreak of World War II and sought to co-operate with the British against Hitler, just like the Yishuv from which it had seceded.
Avraham Stern, however, was murdered in 1942 after a large-scale manhunt in Tel Aviv, and not by the British Army, but by the Palestine Police - the officers in charge were Morton and Wilkins. I believe Lehi later tried to assassinate Morton as a revenge.