This is very strange. The Isle of Man site lists the film as being filmed there. Hmmm... I guess just because they filmed on location at Isle of Man doesn't mean they used their studio. :-/

I just looked at the info on The Dark at the SB fansite, and it also lists them as filming at London's Ealing Studios. Would that be of any use?

http://www.compleatseanbean.com/thedark.html Production info is at the bottom of the page.