Does anybody advise on a cheap accommodation in Dusseldorf?

There is the Hotel Am Spichernplatz. Breakfast is quite well and they have a restaurant of Greek cuisine the next door to them which is also a budget type. Rooms have all the necessary facilities and a free wi-fi. But, if you are very sensitive to any noise things, then you should keep in mind that there are tram and road lines near to the hotel.

One more with good reputation is Air Hotel Wartburg. We were to stay there by accident, but were not disappointed at all. Room was enough spacy and breakfast is saturating, starts at 6.30. You can reach the airport within 10 minutes (so, you can hear all those sounds from the hotel room at night). The exhibition centre is also the next door. The personal is caring.