Nigel, I've done this very recently. If you want to call me I'll tell you exactly. 01622 683044
Basically, just unbolt the caliper and brake hose, remove the old caliper and the disk should virtually fall off, (may need a little persuasion but mine didn't). Then undo the 4 small bolts holding the metal backplate, then using tinsnips or similar, cut a small section out and twist it over the hub. (It's never going back on).
Lastly re-fit disk and check runout, (as described in lengthy descussion previously by Martin & Mycroft;) ). Refit caliper, pads rattleclips and shims. Bleed brakes, bed in for about 50-100 miles.
Test by taking an unsuspecting passenger for a drive without a seatbelt and watch how much effort they need to use to prevent themselves from exiting via the windscreen!