My wife, however, was unwilling to play along with the project, so I used a mannequin bought from eBay as the base ;)
Step 1: Dismantling original PC
Step 2: Preparing the Mannequin
Using a small hacksaw I cut around this seam, with the only issues being the steel mounting points that are meant to be used to secure the mannequin in shop displays. The mounting points in the left leg and neck aren't required, so are removed, and the hole left by the removal of the neck plate is filled to create a power button location.
The nipples that were on the original moulding were also unwanted, so were filed off, filled and sanded smooth.
Step 3: Fitting the components
The motherboard mounting points (as made in step 1) were affixed to the inside of the case using a mix of epoxy resin and polyfilla, to a consistency of something like blutak.
After painting, the PC parts were refitted, and then a cheap chainmail bikini from eBay was added, partly to hold the two parts of the case together, but also just to finish off "the look"....