Continuity mistake: In the scene where Thora Birch's character goes to a café with her psychologist, the psychologist takes a bite of a cake and puts it back on the table. In the next scene, the cake has not been touched.
Continuity mistake: When Liz and her psychiatrist are driving in the blue car to Liz's house for the first time, you can see from the outside-the-car-shot that the roof of the cabrio-car is closed, but when we see a shot from inside the car, you can see in the left top corner of the screen that the car-roof is open, later it's closed again.
Continuity mistake: When all four are in the bunker, Mike says, "I'm having sausages with Liz, tonight", and in this shot Liz sits down then puts the pack of sausages on the floor but in the following shot they appear back in her hand. (00:22:55)
Continuity mistake: When Liz is in the cottage just before Martin arrives looking for an explanation, a woman leaves the cottage and walks up to her car. The car's wheel is turned to the right, yet in the following shot from behind Liz, the car's wheel is pointing straight. (Zoom in is required.) (01:00:50)
Continuity mistake: Near the beginning, when Martin is talking to Mike, Frankie and Geoff on the stairs, just after Martin says, "Welcome to my office", in the previous shot Geoff is not leaning on the ledge of the window, but in the face shot he is. (00:14:55)
Continuity mistake: Close to the beginning when the group is waiting for Martin to open the door/hatch, Geoff takes the phone from Francis, and he points it up in the air with his right hand, in the following shot the phone is in his left hand. (00:26:05)
Continuity mistake: When the four of them are in the bunker after they have discovered the bugging devices, Liz shows them a piece of paper with what to say, and in one shot Geoff, to Liz's right, has his hands down, then in the following shot they are raised. (00:36:00)
Continuity mistake: Near the middle of the film when we see the alternate version of events, Frankie answers the phone. Look where her fingers are on the phone in this shot. When the camera cuts to the following shot of Liz drinking out of a bottle, Frankie's fingers on the phone have changed position slightly. (00:42:25)
Continuity mistake: When we first see Mike playing rugby and he catches the ball, in the previous shot all the players are running really fast at him, but in the next shot when he gets tackled by his friend all the players are now stopped and looking at him. (00:08:30)
Continuity mistake: When Liz first meets Dr. Philippa Horwood, they enter a room in the hospital, and Liz goes to a door to have a look inside. When she steps back she is standing next to door and proceeds to close it, yet in the following shot her left arm is outstretched still holding the door. (00:05:30)
Continuity mistake: During the flashback of the true events of what went on in the bunker, Mike and Geoff are trying to get Frankie to have sex with them. When she says "What have you done for me", in one shot she steps away, brushes her hair back, and does a little dance, then in the following shot she does the same thing again. (00:50:35)
Continuity mistake: When Dr. Philippa ends the session with Liz and goes out to her car talking with Tom on the phone, she is facing the front of the car in one shot, then suddenly facing the rear of the car in the following shot. (00:39:25)
Revealing mistake: Just as Liz goes to talk to Mike (where she talks about slitting their wrists with Geoff's knife) Geoff is in the foreground of the shot, covered in a coat/blanket/something, and is supposed to be dead. But you can see his stomach and chest moving as the actor breathes. (01:25:05)
Visible crew/equipment: During Martin's version of events, when Liz says "Remember that place we found and said it would be great for a party" you can briefly see the boom microphone dip into shot above Frankie's head. (00:45:37)
Answer: The Hole, by Cliff Mansell. No idea where to get hold of it.