I think Churchill gave up flying on the orders of Clemmie - in one of Sir Martin Gilbert's volumes there's a letter from WSC in which he rather sheepisly agrees to do what he's told and stop flying. There are times when I rather think that Hitler was fortunate that it was Mr Churchill who was PM rather than Mrs C....
He was also a former 11th Hussars officer, and having commanded a battalion on the western front, quibbles about him wearing army uniform were non-existant. I think he also wore RN uniform on occasions - whether this was completely 'legitimate' or not I'm not certain, but neither George VI or the RN seemed to mind.