So it turns out that it was just a problem of using braces {} where I should have used parens ()
render() {
return (
<ScrollView>
<List>
{
this.state
&& this.state.products
&& this.state.products.map((item) => (
<ListItem
key={item.ProductId}
title={item.ItemCode}
/>)
)
}
</List>
</ScrollView>
);