Hi Skandha, I’ve got it at last!! I think that there was confusion on my part for three reasons;
1) I wasn’t differentiating between the settings for Scroll Bar and Scrollup, hence I didn’t fully pick up what you were saying about the Scrollup setting.
2) In the theme the feature is referred to as Scrollup yet the plugin refers to To Top.
3) When installing the theme it recommends installing the To Top plugin, yet the feature is already built in to the theme, so why recommend it?

Anyway I am there now, sorry for the confusion and thanks for your help.