Hi and thank you for your reply.
You’re right, it appears that my SEO plugin is adding a visual editor and then stripping the tags. Thanks for your help.
@naa986 great, thank you. That looks to be working now.
Thank you, @fajitameatpete, it seemed to work okay for the front end, but prevented me then from editing any of my pages, unfortunately.
I changed the font-family in all instances in style.css, so I’m not sure why it didn’t take. However, adding the code to Additional CSS has sorted things out, thank you!