Hi AndyD ...
... and for all the others, that want to give OS X Server a try to retrieve local sync.
I stopped reading this thread at page 10, maybe someone else posted in the meantime an instruction for OS X Server?
What I found out about the solution with OS X Server 3.0 is the following (and all those, who know better, please correct me):
Since 10.7 OS X Server is no longer a standalone OS but an upgrade to the regular OS X. Likewise the Mac OS X you can get this upgrade in the Mac-Appstore.
Moreover I read, that it runs like an app, which can be started and stoped like any other app - not really sure, if this is true.
There is an overview over the Tech Specs on Apples HP and as well some documentation to the server software.
And, I found in a german forum a short instruction for setting up the necessary services for the local sync between host and clients on the server. It's not necessary to run OS X Server on an extra machine, it also can run on your main working computer. Since this post is good structured, it might help, even if you don't understand German.
apfeltalk.de
All in all not too complex and like the german author of the post says - it works and it works fine!
At the moment I cannot translate it, since it's 5.45 am and I'm too tired, but if there is further interest I can do it and post it the following days -
edit: minor corrections and additions