There are number of good, reasonably priced hotels in Münster city. We have listed a few below for your convenience. You can also book rooms here.
Factory Hotel Münster
Modern hotel, 1,8 kilometers by foot from the workshop/conference location
H4 HOTEL Münster City Centre
Directly in the city center
ibis Münster City
Not far from the city center and very close to the train station
City center, not too far from the train station
B&B Hotel Münster-Hafen
Münster Hafen, not too far from the train station
Please note, the city of Münster charges an accommodation tax of 4.5 % for overnight stays in hotels, vacation apartments and campgrounds. Overnight stays resulting from business trips or training can be exempted. Please present your certificate of attendance at the hotel reception desk.
More information can be found here (the text is in German, but there are a few forms in English).