Just so that you know, as well as the Tuesdays and Thursdays at Trinity Arts Workshop (on Pearse Street, near O'Neils), there is also a Saturday afternoon Life Model session at Trinity Arts Workshop from 2pm til 5pm with Ken facilitating. It's €16.
Also, if you want to know about the United Artists Club. Their website is http://www.dublinarts.com/Home.htm From http://www.dublinarts.com/events.htm it looks like they have life modelling on Wednesdays and Thursdays. There is a phone number on their site where you can get more info.