That recipe was created several years ago and Coopers has since changed their kit line up and packaging, so I'm not sure if it would have been the Australian or English Bitter kit that the recipe was based on. Either should work fine, since the Coopers kits (with perhaps a few exceptions) all have the same original gravity and IBUs (i.e. hop bitterness level).
As has been suggested here, you can substitute another manufacturer's kit. If you brought the recipe to your local shop, the staff will be able to help you pick out what you need.
Welcome to homebrewing! Starting with a post on this forum, means you are very likely to succeed. Let us know how that first batch turns out.