This isn't an answer, but more information as to why the uninstaller might be failing. When I run these manual steps, I see an exception.
> C:\BuildMaster\Service\bmservice.exe UninstallWeb
C:\BuildMaster\Service\bmservice.exe : Error stopping service: Service INEDOBMWEBSRV was not found on computer '.'.
At line:1 char:1
+ C:\BuildMaster\Service\bmservice.exe UninstallWeb
+ CategoryInfo : NotSpecified: (Error stopping ...n computer '.'.:String) , RemoteException
+ FullyQualifiedErrorId : NativeCommandError
Removing INEDOBMWEBSRV service...
Unable to remove service: Object reference not set to an instance of an object.
I think maybe the uninstaller doesn't handle this situation and so stops in the middle?