I never thought about it before but now that you mention it, I can't think of a single well-known British general (aside from Montgomery) since Wellington. And even Montgomery I would have to hedge on the word "great." He did very little that was new and extraordinary. He defeated Rommel by building up the proverbial irresistible force behind the lines at Alamein and literally blasting the Axis from their positions. And even there he wasn't able to contain them, prevent them from withdrawing in good order. The one really daring plan which he had, "Market Garden", was a only partial success at best.
As for the Marshall Plan, every interchange between sovereign nations is, by its nature, political. Each national leader tries, or at least SHOULD try, to get the best possible outcome for his own country. While it may have been hard on Britain and France, I doubt you would find too many Americans who would be disappointed. But my interests don't lie in the political arena. I'm more into the military aspects of the war.
And by the way, Rommel was not a Nazi, not a member of the party. He was a German general/ field marshall, and he supported the leader of his country as far as he could, as is expected of any military commander. But he was never a Nazi. There can be no doubt, though, that he was among the best generals in the war.