[DiggerD21]

Oh, the overpriced Tunnel Club. Been there once and that was enough for me. Are you sure the people you have met were from Hamburg and not from the surrounding areas or from completely elsewhere (I mean, you have been in one of Germany's most famous techno-clubs, so it is surely not uncommon to meet a lot of non-hamburgers there)?
But how do you get the impression it is a blue-collar town? It is actually mixed. There are lots of people working in white-collar jobs, especially in the media and advertising industry. Even most port-related jobs are office-jobs due to the high automation in the port.