Hello @GrahamCox,
I tried to look into your site, but your read only link is not working. I see what you mean on the video. I think the image that you have inside the div is making it look more oval that a circle. Try to make the div into a circle first and then add the image inside making sure that its dimensions don’t exceed that of the div itself. I hope this can help. Also, if you update your read only link maybe I could better help you.