To my understanding Hitler’s army was stretched thin for months in 1941-1942 deep in Soviet territory and Hitler had exhausted his military reserves. Why didn’t the UK take the opportunity to liberate France or attack the German homeland during this time?
The British military was reforming after its prior losses when escaping France in the summer of 1940. Britain was also fighting in North Africa. By 1941/1942 they did not have the capability to fight Germany on its own. Winston Churchill even considered the Nazis invasion of the Soviet Union to be a bit of a blessing, as now their forces were split, and the Soviet Union would ground down a larger share of the German Military.