Most British troops did follow the guidelines in most circumstances because the British had been bombed by Germany, had suffered the might of Germany on it's own civilians. There was always some modicum of respect on the battlefield between the British and German forces, but it wasn't directly translated to our occupation. But, remember, not all people think alike - the British troops were still human. Most, if not all, could not look a child in the eye and not say something, or give a homeless family food. And, of course, a soldier that had been in conflict for six long years - couldn't turn down a 'favour' for just some choclate...
But, none of it mattered because the occupation, on a whole, worked. Germans and Germany were always put in their place, there was no changing that.