Hi Paul, thanks so much for your response.
Unfortunately, this doesn't seem to work for me either. I entered the code into the code injection header as you suggest, then saved, logged out and opened incognito....still nothing displayed.
I actually just want it to appear on one page (https://www.simplehonours.co.nz/study-cb) rather than the whole site, so I tried entering the code via the Advanced Page Settings just for that page and this didn't work either.
I'm wondering if the only way to do this is to somehow view the webpage as HTML code and then add my little bit of code just above the closing header tag. But I'm not sure how to do this, and I don't think Squarespace likes me playing around with the coding as I'm not an advanced user.
Any other advice would be greatly appreciated.