Your Moutain Lion Server comes with a Calendarserver and and Addressbook server.
Activate them, follow the instructions in the manual http://help.apple.com/advancedserveradmin/mac/10.8/#apdD1264A58-01EA-4854-A96D-3 CCAB512E7C2
Then your users can have all their sensitive data on your server.
Thanks for the help
Not sure I have explained myself properly, I already have the server set up and have a local calendar and address book working.
The issue I am having is how to integrate it with the icloud address book and appointments.
I have an appointment at 10.30 with a client, I need to have this show up on all mobile devices and the local network mini's. As it stands I have to put it in twice, once in the icloud calendar and once in the local network calendar. I would like to be able just to add it once and it show on all clients.
I do not get it, why your iphone's do not access the local server?
Your server can offer everything iCloud offers. Get a domainname, FQDN, and server to all your clientes from the server. Then you have all the possibilities of inviting, showing "ocupied", resources, invitations and more.
hope that helps.
I think you can also "subscribe" to iCloud calendars...but I do not know the in and outs of this.