I can only assume by "knocking shop" you mean a place to have sex without the hassle of parents and not a brothel. I wouldn't allow it and that's not even taking into account that some ******* that your niece hardly knows is in your Dad's house. I find it very strange that your niece would even approach your Dad about using his house to **** boys? What on earth is wrong with your family? Are you northern?
LOL, Well anything outside of london is classed as northern to you lot, so in your eyes, i am indeed northern.
My op made it sound like she's a ****, but she isn't. She's 23 and only ever had 3 boyfriends, but whenever she's fell out with one, she's with another within a week, so that tells me she's a bit promiscuous when she wants to be if you know what i mean.

She doesn't sleep about like i made it sound, she's not the type. You would think if you've fell out with a partner, it would take you a while to get over it, find someone else, but not her.
She's currently living at her moms with her 17 year old sister in a 3 bed house. She has her own room there. Now there isn't any bad vibes in the house. They all get along really well. She just wants to borrow these rooms so she can shag her bloke without her mom and sister hearing that's all. I don't want them doing that on my bed or my sofa which is still up in those rooms.
Lately im getting sick of her and my nephew's attitudes. I only hear off them when they want something. It's all take take take and no give.
Another thing is, she moved out her moms place last year to live with her previous bf, but it didn't work out so she moved back to her moms. She's in full time work, got a car and no debts so i don't see why her and her bloke don't just rent somewhere. She's done it before so she can do it again. It's not like it's a scary thought to her.