Upgrade SQL Server 2012 to 2014

I am trying to upgrade a SQL Server running 2012 SP1 to 2014.

Initially, the server was running 2012 RTM. When I first ran the 2014 installer, it said that 2012 SP1 or greater was required, so I installed 2012 SP3. When I started the 2014 installer again, it wouldn't detect any instances installed, and only wanted to update the shared features. I rolled back SP3, then installed 2012 SP1 and I am still experiencing the same issue.

I had a look through the Detail Setup Log, and found the following (I also found the same thing before I removed SP3, but with a different version number, obviously)

(08) 2016-05-26 21:21:37 Slp: Init rule target object: Microsoft.SqlServer.Configuration.SetupExtension.DetectInstalledProductsFacet
(08) 2016-05-26 21:21:37 Slp: Package ID sql_engine_core_inst_SQL11_AnyInstance_Cpu64: Installed - Version: 11.1.3000.0
(08) 2016-05-26 21:21:37 Slp: Package ID sql_as_SQL11_AnyInstance_Cpu64: Installed - Version: 11.1.3000.0
(08) 2016-05-26 21:21:37 Slp: Package ID sql_rs_SQL11_AnyInstance_Cpu64: Installed - Version: 11.1.3000.0
(08) 2016-05-26 21:21:37 Slp: Package ID sql_dq_SQL11_Cpu64: NotInstalled
(08) 2016-05-26 21:21:37 Slp: Package ID sql_dqc_SQL11_Cpu64: Installed - Version: 11.1.3000.0
(08) 2016-05-26 21:21:37 Slp: Package ID sql_ssms_SQL11_Cpu64: Installed - Version: 11.1.3000.0
(08) 2016-05-26 21:21:37 Slp: Package ID sql_tools_SQL11_Cpu64: Installed - Version: 11.1.3000.0
(08) 2016-05-26 21:21:37 Slp: Package ID sql_is_SQL11_Cpu64: Installed - Version: 11.1.3000.0
(08) 2016-05-26 21:21:37 Slp: Package ID sql_rsshp_SQL11_Cpu64: Installed - Version: 11.1.3000.0
(08) 2016-05-26 21:21:37 Slp: The package 'sql_engine_core_inst_SQL11_AnyInstance_Cpu64' exceeds the max version limit, it will not be detected as installed.
(08) 2016-05-26 21:21:37 Slp: The package 'sql_as_SQL11_AnyInstance_Cpu64' exceeds the max version limit, it will not be detected as installed.
(08) 2016-05-26 21:21:37 Slp: The package 'sql_rs_SQL11_AnyInstance_Cpu64' exceeds the max version limit, it will not be detected as installed.
(08) 2016-05-26 21:21:37 Slp: The package 'sql_dqc_SQL11_Cpu64' exceeds the max version limit, it will not be detected as installed.
(08) 2016-05-26 21:21:37 Slp: The package 'sql_ssms_SQL11_Cpu64' exceeds the max version limit, it will not be detected as installed.
(08) 2016-05-26 21:21:37 Slp: The package 'sql_tools_SQL11_Cpu64' exceeds the max version limit, it will not be detected as installed.
(08) 2016-05-26 21:21:37 Slp: The package 'sql_is_SQL11_Cpu64' exceeds the max version limit, it will not be detected as installed.
(08) 2016-05-26 21:21:37 Slp: The package 'sql_rsshp_SQL11_Cpu64' exceeds the max version limit, it will not be detected as installed.

From what I can understand, it's saying that it won't detect my SQL 2012 SP1 install (11.1.3000.0) as "installed", therefore it won't upgrade it. 

I am not sure how to proceed here, and I would really prefer to do an in place upgrade.