Continuity mistake: When talking in the pub, Sarah's hands are around her wine glass or not, depending on the shot.
Continuity mistake: When Mark and Matt go into the changing rooms, after the workout, Matt is getting ready to shower. While Matt is talking to Mark, Mark puts a jumper on, but when he reaches into his locker to get his bag out, he is no longer wearing his jumper, until he puts his bag on his back.
Answer: There's no mistake or joke. The camera simply doesn't create a mirror image (otherwise the writing on the truck would be reversed). When we see Mark, he has a newspaper under his right arm (the viewer's left) and then Jeremy is to his left (the opposite side of the newspaper). In the TV, the newspaper is still under Mark's right arm (the viewer's left). If they were looking in a mirror or reflection, then Mark would be on the other side.
Bishop73