Today I changed the wiper blades on my S-Type.
At first it seems complicated as you cannot pull the wiper arms past the bonnet, leaving you in that head scratching situation.
But on the wiper blade mount there is a small clip underneath which you push upwards as hard as you can and then slide the blade off... with a small wiggle it will come off the arm.
Take off the hose from the washer jet and then when the blade is free you need to take the centre mount clip off (quite hard to get the plastic clip off, use a big headed screw driver to prise it off, but be careful not to break) which as the washer jet attached to it and apply to new blade.
I put 10" and 12" PIAA blades on mine... works a treat
PIAA blades are awesome as they are silicone, i have a few sets in my garage if anyone wants to buy a set.