Embedding Mailchimp code in Gutenberg

Hi,
I can’t seem to get the Mailchimp form embed code to work properly in the Gutenberg editor. I’m pasting the appropriate code into the code editor, but it doesn’t render the form properly when saved, and also makes the code visible on the public page. I’ve noticed that after I’ve pasted the code and saved the page, when I look again at the code, Gutenberg has added <p> tags on most lines.

Can someone work out what’s going wrong? FWIW, I’m using Gutenberg on WP5.02 – part of a University website, so I don’t have complete functionality (eg can’t install plugins).

Thanks,
Cormac