This happened about 20 years ago when I lived in Finchley, North West London. I was living in a flat near Staples Corner with my two children. I was in temporary accommodation, and the block of flats were about circa 1920s.
I was in bed one evening when I heard people chattering and glasses clinking. I looked toward my open bedroom door and saw people milling around and (daft as this may sound) walking out of the toilet and walking past my bedroom door. I remember one lady was dressed in a lovely tight fitting petrol blue 1940's dress. Among them was this tall person dressed as a clown. He moved strategically through the people toward my door, stopping to pose in funny positions every other moment. Finally he stood in my bedroom door, stood up straight then just dropped a pose and just glared at me as if to say, "What you going to do about it?"
I turned away from him, looked at my wall, shut my eyes and then opened them again fully expecting that I was imagining it all. When I looked back at my door he was still there. I shut and opened my eyes again and he was there, but getting fainter, until finally he and the others just vanished.
I wish I could say why such a thing happened. For some reason I wasn't scared, probably because my children were in the room with me! I have had many other experiences over the years but this clown person has always had me baffled.