What I remember is its UK made, one american actress. A group of friends in mansion, lots of drugs and sex, really bizarre plot. People end up dying. Theres one guy whos studying denistry. There a serial killer cult all over the tv news. I remember a picnic scene and a cow or bull. I feel like it was a cross between the Young Ones and Trainspotting? Been searching for years, asked all my English and Irish friends they have no idea?
You might be looking for Shallow Grave (1994).
Had me excited for a minute but thats not is, this is far more surreal and obscure than Shallow Grave. Thanx though for the effort.