Hi,
You need to remove the top yolk in order to get access to the securing screws that hold the switch in place.
The loom to the switch will also need to be unplugged.
The 2 screws securing the switch are anti tamper where the heads shear off when they are installed to stop unpleasant types removing your ignition switch without your permission.
You will need to drill these out carefully before the switch can be removed from the yolk for whatever reason.
Make sure you purchase new anti tamper screws and a small torx drive socket to fit them on instillation.
Hope this helps
Greenisbest, October 2009