It never fails to amaze me how indiscreet clients can be when they visit you for incalls.
My flat is on the ground floor. Therefore when the client rings to say they are at the nearby tube station, I will tell them that I'm ground floor, and that I will buzz them in and open my flat door immediately to let them in. It astounds me the number of men who will exclaim at the top of their voices, "Hello Simone, it's so good to meet you", and then try and continue a line of conversation that just screams 'PROSSIE ALERT' to all and sundry
I have no hesitation at all in asking them (very nicely) to keep the noise down. Even if it means putting my finger to my mouth, and going 'ssshhhhhh'. I've even been known to ask clients in the throws of passion to drop the racket a few decibels. Any half sensible man should appreciate your need to be discreet, and anybody who winges about it isn't the sort of guy I want to see again anyway. The risk of getting thrown out of my flat far outweighs my worry about slightly offending a client.
Today I actually had a client I only saw a week ago try and walk up the stairs in my building! How he couldn't remember I live on the ground floor after such a short space of time I will never know! It's simply amazing sometimes.
Every tenancy agreement I've ever seen has the 'immoral purposes' clause in it. So basically you need to be VERY careful you don't get caught out. I'm afraid the shared bathroom thing could prove to be a problem. I simply couldn't imagine working from a flat with a shared bathroom. You are going to have to be extra, extra careful to ensure there are no comings and goings when you let your client into the bathroom. Also consider limiting the number of incalls you do. Less clients equals less risk of getting rumbled.