I found this bit of info on the Technet Forums which solved my problem.
Actually there is a workaround to get this to work without installing SQL. It all has to do with the way the topology builder work – enabling or disabling changes in topology during install do not work after the first attempt. After installation this works fine as the CMS is up and manages topology changes.
To get step 2 to work properly you need to manually re-assign the topology to the localstore – i.e. what step 1 does by doing the followng:
•Export-CsConfiguration –FileName <ZIP file to store the exported configuration>
•Import-CsConfiguration –FileName <ZIP file storing the exported configuration> –LocalStore
Export-CsConfiguration will read the configuration and store it in a ZIP file. The Import-CsConfiguration with the –LocalStore switch will import the configuration in the local replica of CMS .
Then run item 2 .. this should allow the install to complete.. deciding on what you want to do with the archiving and monitoring datastore can be dealt with later .. at least Lync is now up.