Are you being severed?
I feel I am qualified to comment on this, seeing as my wife is German.
The important thing for Brits to understand is that while you are always ready for a joke or witticism, most Germans are not. They don't understand British humour because they are not in a state of mind to enjoy it, and often think of British humour as either overly dull (in the case of a sarcastic comment about your kids' good behaviour) or (in the case of stuff like Monty Python), hopelessly silly. That being said, I *do* know a few Germans who love Monty Python, just as I know a few English people who utterly despise it.
For most Germans, there is a time and a place for jokes. That is usually with friends, or people you know fairly well. With strangers, it tends to go down like a lead balloon, on most occasions. That is probably why most Brits, eager to tickle Deutschland's funnybone, have come back with the erroneous impression that the nation of beer and premium car marques has about as much a sense of humour as the Borg collective.
Even other nations have fallen into the trap of seeing Germans as humourless bits of meat on two legs: A colleague from the Netherlands was convinced that my German boss had no sense of humour, and was actually scared to crack a joke with him. (It did not help that my boss happened to dress very professionally all the time - it made him look like an FBI agent.) But he was quite happy to crack (or enjoy) a joke with most of the German office staff.
But then again, the Dutch are a different crowd: When I went to work for a well-known Dutch bank in Amsterdam in 2008, the team leader asked me where I was from. When I replied that I lived in Germany, he snapped his heels together, saluted me dramatically and exclaimed "Heil Hitler!" Yes, this was a bank. Yes, these were grown men. But then again, the Dutch sense of humour is, shall we say ... robust.