Blimey Al, even as someone who also likes a head on their pint, I think 3/4" is going some! Personally, I think just under a centimetre is perfection and if the barman is particularly skillful, with a slight convex curve on the top.
Surprised none of our southern contributors have pulled you up on the flat pints point. ( I know Quinno and rpadam are vehemently anti-sparkler). There is, of course, a huge difference between headless beer and flat beer. The accepted wisdom is that southern brewed beers are served in a livelier natural condition than those in the north and form a natural looser head, on pulling. However, I have to say I think some southern pubs overstep the mark and use the headless argument to serve ales (past their best) as lively as tap water. Step forward the Market Porter, Charles Dickens, Duchess of Cambridge, to name but three.