Get a decent sized basment type room and cover it in plastic sheeting. Get shit loads of egg boxes and get the bugger sound proofed.
Get the wench into the basment and have a bit of fun before disposal. I recommend slicing off eylids for starters, she can't close her eyes to try and seperate herself from the pain your gonna put her through.
The I would go for a decent knife, weged under the knee-cap and apply pressure. I always thought the sound would be like a suction cap coming away from a window, untill the inevitable 'pop' as the knee-cap dislocates itself from the knee and is free floating around under the skin. After that a good deal of slicing of dangly bits off the body would cheer me up no end.
Once a good deal of fun has been had I would wrap the remains of the wench in the plastic sheeting as I took it from the walls. All remains, egg-boxes etc would get wrapped up so there would be nothing left apart from a mass of stuff in plastic sheeting.
Take this mass of sheeting and, under cover of darkness, put in the footwell of the back of the car, to give proper weight distribution in the car, fooling any on-lookers.
Now, I'm not RA so I would have to do a bit of research but I would try and find the land where the AS90 or any other Artillery pieces carry out their range work.
Wait for a nice night then bury the plastic mass about 2-3 feet under the main impact area.
Retire to the gentleman's club for choice cigars and fine port.