I like the grid but ignored Percival as a P.M. as it is Perceval.

Very good, and solvable in just over two minutes, but there are several equally valid solutions, as Churchill could swap into the PM's group, with May, Wilson or Baldwin (though he was fictional) swapping into the famous Michaels group, and Crawford moving to take Churchill's place in the Landscape features group. The easiest way to make it work like a proper wall would be to change Crawford for something else.