I too had the same situation at the airport (sorry I am normally a lurker, but had to throw in my 2 cents). They asked if I was visiting anyone--I answered honestly, "yes," but I was there for sight-seeing also. Well, that brought on several questions, which caught me off-guard, as I had never been asked them before. He asked how I knew my friend (who is male and an English citizen), and he asked me if it was romantic (we're just friends, and I have visited before, and have traveled pretty extensively, so i was surprised), and he asked me where I would be staying (with my friend or a hotel--I was staying at a hotel), and how much money I had allotted for my visit, where I worked and what my job was, etc. I travel in and out of Germany once a year, and I never get any questions--barely a passing glance (and i am visiting friends-not business), but maybe he was just curious/cautious. But I had never been asked those questions entering the UK before, and I was a bit embarrassed. He was pleasant, but direct!
Just my experience-katy