Went to a lunchtime class taught by Gerard Blaize, 7th dan. There were just over 25 people training, of which only about 5 including myself were not in hakamas! For me, that felt like a large class, especially for a lunchtime. The very very advanced level of training felt a little daunting at first, especially as a complete new firstime visitor to the dojo. However, everyone was relaxed, friendly, welcoming, and the training was inspiring and educational. Despite the language barrier, it was really wonderful. All in all, quite exhilarating.
They have classes 5 days a week, including various lunchtimes, see their website for details. Additional useful info:

Nearest Metro stop is Gare de l’Est

Phone: 01.48.24.50.70 or 01.46.37.24.91