The yoga classes are given in the gymnastics hall of the elementary school "Lucas van Leyden" (Sint Ursulasteeg 28). You can ring the bell at the blue door in the "Caeciliastraat", then I will come to open the door for you. It may take a while before I am there to open it, because the gymnastics hall is at the first floor of the building.
There are also changing rooms. The doors are open as from 15 minutes before the beginning of each class.