We reached Hamburg about 6.30 pm and went straight to the Hotel Bellevue. Unfortunately they are as unscrupulous as airlines and had considerably overbooked so we were moved to the Holiday Inn 3 miles away, which is very nice but in the wrong place for photos.
After all the to-ing and fro-ing we eventually started taking photos after 8 pm (having lost well over an hour) and carried on until after 10 pm. Mainly around the Rathaus and the inner lake. The Rathaus is enormous and even with my 43 mm lens on my Mamiya (like a 21 mm on a 35 mm camera) I still couldn't fit it all in. I used exposure times between 2 and 30 seconds at f5.6 depending on how bright the subject.
Moral of the story: avoid the Relaxa Hotel Bellevue in Hamburg like the plague if you want to be sure the room you book will actually be available when you turn up.