Figured the problem. Hopefully this can help someone. I never mentioned in my question that I was using a hybrid graphics set up with a 7730 AND an Intel 4000. When you plug in a separate monitor you get a mad flickering action going on. A temporary solution someone found is listed here.
This worked a treat initially, however when I opened the display options and moved my external monitor to the right hand side of my laptop screen that's when the problem happened. I looked at the command I used to stop the initial screen flickering:
xrandr --output VGA1 --auto --left-of LVDS1 --output VGA1 --scale 1.0001x1.0001
I noticed the bit that said
--left-of. This would be fine if the monitor was to the left of the main display but it no longer is! Your command should simply be
xrandr --output VGA1 --auto --right-of LVDS1 --output VGA1 --scale 1.0001x1.0001
and everything should be working fine.