Yes, it's based on real events and people. But like many movies based on true stories, there might be some creative liberties taken for dramatic effect.
A possible theme could be the concept of home. 22 Hyde Park Gate is a specific place that could be seen as a home in the story. The story might explore what makes a place a home, whether it's the physical building, the people in it, or the memories associated with it. It could also deal with themes of belonging or not belonging, like a character who feels out of place in this seemingly posh area of Hyde Park Gate, or characters who are deeply rooted and feel a strong sense of belonging to the place.
I'm not sure specifically which '22 Hyde Park Gate short story' you are referring to. There could be many short stories related to that location. It might be a story about the people who live or have lived there, or perhaps an event that took place at 22 Hyde Park Gate.
Hostel isn't based on any true events. It's a product of the filmmaker's imagination and designed to entertain with its horror elements and plot twists.
Yes, I once stayed in a hostel where the room was freezing cold at night. The heater wasn't working, and when I asked the staff about it, they just said there was nothing they could do. It was so uncomfortable that I barely got any sleep that night.