In the party scene cast actually got drunk playing drinking games in 15 minutes.
Some of the cast were convinced there was a ghost in the house they stayed in during the shoot because other members kept leaving towels and empty bottles outside doors, turning furniture around and hiding things.
Filmed in 8 days.
Cast and crew had a war whereby the losers would have to shoot the last scene in just their underwear. It got very competitive, but luckily it didn't happen as the shoot took place in the Lake District in December.