Using photographic shadows

I need to use an object and a shadow shot in a studio shoot. It was shot on a light cream background and I need to piece the object and shadow back together and then place on a bright coloured background.

I've tried the background eraser but the quality isn't good enough, what can I try next.

use the magic wand
click the light cream background (but you need to set first the threshold of the magic wand according to you desire on which part of the shadow should be left out)
delete the selection made by magic wand and you'll be left with shadow itself and more realistic of course.
you can also feather the selection before deleting it

Also this may help. Bear in mind that when using the magic wand tool, you can hold down CTRL to select multiple areas (and clicking), and click and hold ALT to deselect areas.