3 other methods.
1) Drop the engine and climb into the boot like a monkey to release the rear windscreen
(don't forget a good diet before proceeding)
2) Go with your hand under the rear wing (on the side of the cable). You should be able to catch the cable housing. Pull it down and it should release everything
3) Spray plenty of rust release more efficient than WD40 on the 2 window holders. Take mole grips and turn them of 90°. It will pop open
Of course the first method is a joke. I only used it once on an engineless car