The Haunting of Berkeley Square

Based on the terrifying 'true' stories.
Four students enter the fabled 50 Berkeley Square in order to spend the night and gain enough research to write their Masters theses. They want to find ghosts, want to prove the existence of them. They do not cower at the things that go bump in the night, but run to them. Wish to document them.
And they find what they are looking for, more than they could have dreaded. For as the night stretches on and the ghosts of the House torment them, something else is coming.
An ancient evil that makes that House its home.
There's something in the cellar and IT is rising.