Plattenhof hotel is extremely well located. It is 5 minutes by tram from the central station and there is a tram that takes you directly. One tram stop away and you will get to the main building of ETH which is absolutely impressive and their terrace offers a stunning panoramic view of the city and the area. You also have a direct connection to the Kunsthaus which you must not miss.
This listing describes a small room, but if you are booking for shorter times, you will most likely be treated like other hotel guests, pending availability. I got a regular hotel room so there were no fuss about the toilet.