Because you will get much better rates booking on the internet, we recommend that you use one of the following websites to make your hotel reservation
You can also google the following key words : hotel paris marais
On most websites, the area you need to ask for is MARAIS. On some sites (booking.com for instance) it is called CENTRE POMPIDOU, or BASTILLE, or even RÉPUBLIQUE. The arrondissement is the 4th. (A hotel in the the 3d or 5th arrondissement would also be within walking distance from the conference venue, though slightly further.)
You will find plenty of 3-star hotels in the Marais. Two-star hotels are harder to find which is why I suggest the following two.
The recently renovated 2 star Hotel Jeanne d'Arc
The Hotel Saint-Louis Marais
which is on the same street as the university, a 45-second walk.
The MIJE youth hostels are located in the Marais, very near the conference venue.
Finally, you may be eligible for accomodation at the Centre culturel irlandais / Irish College, right across the Seine.