So whilst in the process of attempting to install the March PU for SharePoint 2013, the SharePoint Technologies Config wizard seemed to be taking a very long time to complete. So long in fact that it never completed and just seemed to be hung on Step 9 of 10, upgrading SharePoint 2013.
Looking at the pcsdiagnostic logs there were a lot of the following events, and pretty much nothing else:
SyncUpgradeTimerJob: sleeping for 10 seconds
No matter how many times I reran the wizard the same thing happened. However, running the following command forced the upgrade through:
C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\15\BIN>psconfig.exe -cmd upgrade -inplace b2b -wait –force
After this I reran the Config wizard again (just to be sure) and the farm was finally upgraded.