I did indeed comment out the Render entry.
The only thing I didn't comment out was the [sdkEngine.sdkEngine] - though I commented out the entry under that heading which was ;SceneManager=sdkExeEngine.sdkExeSceneManager. So could it be that leaving [sdkEngine.sdkEngine] resulted in the game using that?
I should say that I have now moved all the sdkEngine/sdkCore files off the UT path and so the game now uses Engine.Engine.