Correct. I solved the style problem in the settings (hadn’t thought to look through those!) and changed it from full styling to something else.
But the calendar didn’t integrate well with our site – because it doesn’t use a shortcode, I couldn’t configure our top banner to say “events” (it normally says the page title), and the page title as it appears in the firefox tab was just the URL and not the site title. So I’ve moved to a different plugin, it has less features (and I had to bodge-code a widget to show upcoming events in the sidebar), but integrates fully with a shortcode, and looks neat.
Thanks for looking though!