"On the very rare occasions I've tried computer monitorsor TV screens in my renders I've used ambient. Any specific reason you use translucence instead?"

No, they seem to be identical in brightness and projected light. It mainly came about because I made a mistake once setting up a monitor to render (the image was linked to diffuse so I just set ambient to white and gave it a low value. Needless to say the image didn't 'glow' that well and washed it out so I plugged it in to translucence, turned off ambient and it worked). I'm sure ambient is more technically correct, but to date translucence has worked as intended, and that's as much as I ask.