Last time I checked, the English language developed in England. The UK is a group of several countries, most of which had or have a different language to english before they were "conquered", similar in the way which the US got English as its language.

So if the "Whinging Pom" wants to get padantic, you need the English flag, not the UK flag. (The english flag from memory is a red cross on a white background, the UK flag is the british flag which is the Union jack - but I could be wrong, coz I dont care enough to check!)