I don't think CN Ombudsman would step in unless the hotel was unresponsive. I think writing the GM first is an essential initial step. This is weird -- even if there are cultural differences, they certainly should be sensitive to this situation in a hotel in a major European city!

When we had a problem with this hotel on a points stay some years back, though less serious than this sounds, the GM did come through then, so I'd say that contacting the GM is the correct step.