This is a typical low-budget British movie: in other words, it's a fairly competent idea rushed into production without much thought on the script. While there's little original in the storyline (in fact, the whole plot felt very similar to 'Sorority House Massacre 2', even to the extent of the flash-forward at the start... except that unfortunately the hot girl from 'Quills' doesn't spend the whole movie running around in a nighty), it does have a couple of scares and some laughs, a few of which even seemed intentional.
I was impressed with the first minute or so, since I thought for once that there might be a new British director with some sense of style; but then it went into ten minutes of tedious, annoying reminiscing by ex-public-school yuppies which was irritating at best and left me just wishing they'd hurry up and die. It also exposed the limited acting abilities of some of the cast who were unconvincing even in such simple roles. Once the main character actually arrived, which seemed to be around fifteen minutes into the movie, things started to move and the rest wasn't too bad until the monologue at the end which basically invalidated most of what had gone before.
So there's not a lot that can be done to salvage the plot or the often predictable 'surprises' (there's a killer in the house, someone very obviously sits by a large window, guess what happens next?), but cut out that monologue and the boring fifteen minutes and it could be a half-decent late-night Channel 5 movie.
And _any_ movie with that girl from 'Quills' is worth watching at least once...