You will need torx to do other work on your disco in the future. Just go to an autoparts store and buy a small set of torx at least from 15 to 30.
If you don't want to buy another set later, then go ahead and spend a few bucks more and get a "security torx" set. Some torx bolts on your disco are going to be security. NOt the parts you are about to change, but say you wanted to replace a horn button (I have replaced 2), then you will need a security torx set. Basically, the only different is that the tip of the torx will have a small hole drilled in it. They work on non security bolts as well, of course.
I think I paid like $7 for a set of 8 or 10 from Checkers.