Early on, McGill changes into a blue turtleneck. The next scene, it's brown. The next scene, it's blue. It changes again to brown.
An shot of an ice cream van being chased by children appears twice.
When the post card drops through McGill's letterbox, there is a stamp and his name and address on it (side 1).
When it lands on the floor, it is an advertisement for life insurance (side 2).
When McGill picks it and reads it, the side towards the camera is blank.
McGill's address is shown as both Flat 7, 56 Clive Mansions, [London] SW3 and Flat 7, Kingston Court, [London] SW7 (on the postcard).
What about the blond girl? She wasn't dealt with or part of the attackers in the end.
Why would they assume McGill was home? A drunken Willard could just have easily turned the lights on and opened the curtains.