I watched 'When the lights went out' today - I thought it was great. It doesn't get very good reviews on 'rotten tomatoes' for example. But that's probably because it's so quintessentially British. It rolls along at a rather sedate pace and there's not much in the way of ghastly special effects and screaming. But the attention to 1970s detail is amazing. The decor, the crockery, but down to the door handles and the hair bobbles, for god's sake, and many other subtle things. It's proper time travel and whoever did the props did an amazing job. I found the exorcism scene with people exclaiming 'flippin heck' and the general term of abuse being 'bugger off' to be marvellously British. I liked the way it was sort of ambiguous to start with, with the mention that the girl had played tricks before (what with poltergeists generally getting blamed on girls pulling tricks). And that after the exorcism they signified she had grown up, by giving her a grown up hair-do in the salon.
I don't know how closely it matches the real events if at all. But I enjoyed the film. If you're not hoping for some US style paranormal extravaganza you might like it too.