The other reason you can't use the ST170 space saver on the front of the car is because of the Quaife diff..................it does all manner of strange and unpredictable things if you put different sized wheels on either side of it!

As mentioned, 5th RS alloy is ideal but won't fit in the boot space so ST170 space saver is your next best option but can only be used on the rear, JUST what you need if you do get a front puncture in the middle of the night in the pissing rain