Can't uninstall SQL Server 2008 R2 Express

Hi all,
I have unfortunately let myself be persuaded (by a company selling a solution to us) to install SQL Server 2008 R2 Express on a Windows 2012 Standard Server.
At first it didn't work, the installation wizard told me to reboot the server - so I did. No change the checklist stopped at the same thing again telling me to reboot first...
Found out that I could install by using this command: SQLEXPR_x64_ENU.exe /SkipRules=RebootRequiredCheck /ACTION=install
Seemed to work, all fine! Rebooted and tried to install SQLManagmentStudio_x64_ENU.exe and got a compability warning saying that the SQL Server 2008 R2 Express is not compatible with Windows 2012 Standard Server. 
I thought "Right, uninstall it and then install a new and compatible version" Can't uninstall!!
It stops with this error and nothing happens uninstall wise:
Windows Features
The following feature couln't be installed:
.NET ...