Tired of my mother's obnoxious behavior at night

My mother got a new boyfriend about 10 months ago. For the the past 6 months he has been staying over at least one night a week. This has now been increasing to about 2 nights a week. And, I am starting to get extremely fed up and angry with it. They like to have sex late at night. Last night it went until 1 AM. The problem is that we live in a small house with very thin walls, which means my sister and I can hear them going at it. We hate it. It's disgusting. And, because they only do it late at night, we can't even just leave the house and go for a walk or something. (We are both young women, and it would be stupid and dangerous for us to go out walking late at night. Plus the weather is getting colder and it will soon be too cold to go walking when it is dark.) 

Furthermore, it keeps us awake late at night. Both of us try to listen to audio books so that we don't have to hear them having sex. But, we don't want to be listening to audio books at 1 AM. We want to be asleep. If this wasn't bad enough, every time her boyfriend stays over he also gets up at around 6:30 AM. This means we are woken up by his alarm clock, and then usually are kept awake by my mother and him crashing and bashing around the house as they go to the toilet, have breakfast, and etc. It's just obnoxious.

At this point, I don't know what to do. My sister and I have both told are mother that we can hear her, that it keeps us awake and that we don't like it. But, she doesn't seem to care. She has said, "We'll be quieter." But, that is it. I understand that she wants to have sex with him, but I don't understand why it always has to be in the middle of the night. If she did it during the day, then my sister and I could at least leave and go somewhere else. And, we wouldn't be kept up until 1 AM. Plus I think it is disrespectful to the neighbors as well as us because we are in a terrace house and have neighbors on both sides.

What am I supposed to do? I feel like I might just lose control over my temper and unleash my fury on my mother but I know that will only result in her getting pissed off with me. And, she is making my sister really unwell with stress about this issue.

Does anyone have any advice?