Done some checking and the disco 3 wheels are the same as the range rover 3 and sport so they will fit, but they have to have the correct wheel nuts (disco 3 nuts) to suit the wheels. The spigot rings are also required or they will vibrate.
If you are going to get spigot rings go for the aluminium ones the plastic ones can get damaged easy when removing and replacing the wheels.
Another thing i did when using the aluminium rings is smear some copper slip on the inner and outer faces of the rings to stop them sticking to the hub or wheel, and remember if you are carrying the original disco 2 spare to carry a set of wheel nuts to suit that wheel.
All the best
Mark