I suggest that you use the FOSS gerbv package to check your Gerbers as recommended in the Tutorial.

@andyfierman I'm not concerned about the Gerbers - it's the component placement that I need to check, as I've had at least one component (fortunately an SOT23-5, so it was glaringly obvious) where the EasyEDA footprint didn't match the JLC placement orientation.

@david.knell, It was your less than reassuring statement that: "The Gerber preview is there and (more-or-less) fine. " that set my Gerber Viewer alarm bells ringing. :)