If you pass the selection you'll be welcome. BA has a long history of employing non-Brits and you'll find no petty nationalistic tendencies here. Amongst the nationalities I know of flying for BA are Irish, French, Belgians, Dutch, Finns, Iraqis, Canadians Australians and South Africans. I'm sure there are many more I've yet to meet. We also employ cabin crew from just about every country you can think of in the EU - including Germany. Just don't try to get first break by putting your towel on the bunk!
(Thats humour by the way, just in case it doesn't translate)