Thanks for the tips. It turned out that I have had very little free time and I have been travelling a lot of weekends either for work or to go home for Christmas so I have only managed to attend two events so far: Colour Up Your Weekend (Cologne) and NRW Salsa Gala (Mülheim an der Ruhr).
CUYW was a lot smaller than I expected, given the month I went it was a event spread over the weekend. This may have had something to do with the confusion around where the Saturday night was taking place. I turned up at the wrong place initially as it wasn't very clear from the Facebook event that the Saturday night was in a different place from the workshops and the Sunday night but after 5-10 minutes talking with the staff at Club Bahnhof Ehrenfeld I found out the actual location. They said many people had been asking about salsa all night so I suspect a lot of people gave up.
It was a nice venue, with a good floor, friendly people and very reasonably priced drinks. The biggest problem I had was parking (I hired a car for the trip to Cologne as there was no night train to get me home after the event). There are very few empty spaces for street parking in the cityand it took me an hour to find one that was 20 minutes' walk from the wrong venue! I was very lucky in finding a space less than 5 minutes' walk from the correct venue in the end.
The venue for the NRW Salsa Gala was amazing. If you ever see an event held in the Stadthalle Mülheim it is a must. The floor was one of the best I have ever seen, with plenty of space even with a large attendance. Lots of Dutch dancers made the trip over the border for this event and there were a lot of good partners to be found. The music wasn't always to my taste but I would definitely attend the event again.
Next weekend I'm visiting friend in Berlin and the weekend after I will be at the SOS weekender in London so I'm not sure when I will next have time for dancing in NRW (Nordrhine-Westfalen - the region that contains Dortmund, Cologne, Bonn, Essen, Münster and Mülheim)