Yes, you'll need a #4 pozi to shift the disk-retaining screw...
Wera Extra Tough Pozi #4 32mm - Screwfix.com, Where the Trade Buys
See also
http://www.landyzone.co.uk/lz/f8/disco-2-td5-brake-disks-pads-bleeding-44852.html
It's a pretty easy job. Wheel off. Remove the 2 smaller bolts on...