In the p.s. configuration, there's one lav for the 26 C class seats, and two for the 72 Y seats - slightly better ratio in C, but if there's one person taking a long time, it gets tied up. One time I ended up heading to the back to use the Y lav (both empty) because I had to go and lost hope the person in the C lav would ever come out. When I got back to my seat (8A), one of the FA's came over and gently reminded me that C had its own lav.