Buchanan, like many Irish Catholics (including Joe P. Kennedy), had a hatred for all things British, They would have loved seeing the swastika flying over Buckingham Palace.
You bet. Kennedy is a great example.
I identify with my own Irish Catholic ancestry (although I am also partially English, German and Scots-Irish). I am not fond of the Brits because of their centuries long oppression of the Irish and since Henry VIII of Irish Catholics. That does not mean that I would have "loved seeing the swastika flying over Buckingham Palace."
George VI's wife was a particularly cherished heroine of freedom during the war. Churchill was an inspiration to the entire West. Chamberlain was a bum and rightly relegated to the ash heap of history. It is not as simple as you suggest.