Google Play Games Integration issue - CommandInvokationFailure: Failed to re-package resources.

So, I've imported the latest Google Play Games package from GitHub and followed the initial setup instructions.

Problem is when I try to build I get the error :-

CommandInvokationFailure: Failed to re-package resources.

As per console message :-

 CommandInvokationFailure: Failed to re-package resources.
 D:\Program Files\Android\android-sdk\build-tools\27.0.1\aapt.exe package --auto-add-overlay -v -f -m -J "gen" -M "AndroidManifest.xml" -S "res" -I "D:/Program Files/Android/android-sdk\platforms\android-27\android.jar" -F bin/resources.ap_ --extra-packages com.google.example.games.mainlibproj:com.unity3d.ads -S "E:\Users\Administrator\Documents\CircleBreakout\Temp\StagingArea\android-libraries\unity-ads\res"
 
 stderr[
 AndroidManifest.xml:21: error: Error: No resource found that matches the given name (at 'value' with value '@integer/google_play_services_version').
 
 ]
 stdout[
 Configurations:
  (default)
 
 Files:
   AndroidManifest.xml
     Src: () AndroidManifest.xml
 
 Resource Dirs:
 Including resources from package: D:\Program Files\Android\android-sdk\platforms\android-27\android.jar
 applyFileOverlay for drawable
 trying overlaySet Key=app_banner.png
 trying overlaySet Key=app_icon.png
 applyFileOverlay for layout
 applyFileOverlay for anim
 applyFileOverlay for animator
 applyFileOverlay for interpolator
 applyFileOverlay for transition
 applyFileOverlay for xml
 applyFileOverlay for raw
 applyFileOverlay for color
 applyFileOverlay for menu
 applyFileOverlay for font
 applyFileOverlay for mipmap
 Processing image: res\drawable-xhdpi\app_banner.png
 Processing image: res\drawable-mdpi\app_icon.png
     (processed image res\drawable-mdpi\app_icon.png: 90% size of source)
     (processed image res\drawable-xhdpi\app_banner.png: 93% size of source)
     (new resource id app_banner from xhdpi-v4\drawable\app_banner.png #generated)
     (new resource id app_icon from mdpi-v4\drawable\app_icon.png #generated)
 ]
 exit code: 1
 UnityEditor.Android.Command.Run (System.Diagnostics.ProcessStartInfo psi, UnityEditor.Android.WaitingForProcessToExit waitingForProcessToExit, System.String errorMsg)
 UnityEditor.Android.PostProcessor.Tasks.TasksCommon.Exec (System.String command, System.String args, System.String workingdir, System.String errorMsg, Int32 retriesOnFailure)
 UnityEditor.HostView:OnGUI()

I've spent a lot of time searching through solutions but none have worked.

Any help greatly appreciated.