>(the prop has also spun off once to my horror!)

The engine threw the prop because it is a four-stroke and it was a bit lean. Nothing to do with the electric starter.

>The prop is attached using a Great Planes aluminium safety prop nut.

If you are not using the stock OS double locknut and are securing the prop with a prop nut/spinner thsi could be a safety issue. Four strokes can and do backfire and can throw props and need the double lcoknut.