Well, managed to get the desk to within 2 cm of central to the wall by covering the right hand socket I didn’t use.

Monitor arm has been lowered, and as it does so, it moves to the left; am now 2cm off central to the wall, so the track art will look spot on.

Why I hadn’t thought of it earlier I have no idea. Think this thread helped inspire my creativity / desire to not spend more than I had to.

Still want a new monitor though!