SQL Server Service refusing to start

Have attempted a number of things to get this service (SQL Server (MSSQLSERVER)) started without any luck

• Attempted to start service with local admin, domain admin, separate admin & standard accounts
• Attempted to change logon account for the service.
• Could not see any anomaly in Process Monitor
• SQLcmd throws an access denied, despite having full domain admin and local admin group AND EVERYONE as full control. SYSTEM by default has full control.
• Attempted to 'repair' the SQL instance, throws up this error several times:

Attempted to perform an unauthorized operation

The error i get when attempting to start the service:

The SQL Server (MSSQLSERVER) service failed to start due to the following error: Access is denied

The SQL Server Reporting Services (MSSQLSERVER) service failed to start due to the following error: Access is denied

There are no other error codes. All SQL services except the SQL Server Browser and SQL Server VSS Writer is dependent on MSSQLSERVER starting up correctly.

Running SQL Server 2012 SP1 CU2 on Window Server 2012. Service was fully working before a reboot, no Window Updates has been applied.

So anything else i could try?