Thanks so much for your help. Your advice worked perfectly for getting the arms to show above the desk.
When it comes to the reflection, if I’m understanding you right I need a separate composition with just the inverted character (2d) and a copy of the camera. Then I would put this comp into my main timeline. After this I’m a bit confused as to how I then use this as the matte. Currently the layers are:
arms
desk matte (alpha inv arms)
No matter how I arrange it, I can’t seem to successfully add the reflection into the mix. If the camera angle changes, do I need separate comps each time this happens with the reflection and camera copy?
Thanks again for your help,
Gareth