The cup moved from the mouse to the monitor when Roy asked him to show the picture from the cup.
When Roy is trapped under the desks, the two women switch positions in between shots. The blonde starts out next to the hall but finishes the scene closest to the window.
A possible goof is when Richmond gives Denholm's mother a Cradle of Filth CD, he recommends track 4 and says that it is called "Coffin Fodder". Coffin Fodder is in fact track 9 on the album "Nymphetamine". However The CD Richmond proffers is not identified because it's gift-wrapped, so it's perfectly possible that the CD is a compilation that Richmond has made. There's no explicit identification of the CD as a copy of Nymphetamine.