first i had heard that they may have offered a comprehensive end to the war."
From the beginning of the war in 1939, the Nazis had offered to stop the war, even including some pull-back from current positions, but always with Germany keeping most of what it had conquered.
At one point (early 1940), some German generals (i.e., Ludwig Beck) had even offered to overthrow Hitler, in exchange for peace and Germany keeping most of it's gains.
The British rejected all such offers, insisting that not only must Hitler be overthrown, but Germany must withdraw from all conquered territories.
In February 1943, with Churchill at Casablanca, President Roosevelt ended all possibility of a negotiated peace by setting his terms as "Unconditional Surrender".