A "Hooray Henry" is an upper class twit with a loud mouth. It is usually used about drunken howling idiots at posh races, or just moronic upper class fools in general, with red cheeks and White Cliffs of Dover foreheads, and bad genetic traits. My father used to use it, so that would mean pre-World War II British slang. "He's a Hooray Henry sort of chap, not too strong on the grey matter, but knows his way around a champagne cork, just." That sort of thing.
pip, pip, Peter T.