I watched a film years ago with my mother one of those ones on really late. Can't remember much about it but there was a girl she buys a flat she has some work done it it, the builder has without her knowledge buit a flat with the flat and living in the walls. The only other thing a can remember is that there is a window with an eye in it. Can anyone help?

I think name of the movie is "Crawl Space"

Might also be Through the Eyes of a Killer (http://www.imdb.com/title/tt0105583/).