Rashida thanks for your reply. Unfortunately SP3 is definitely NOT working with php8.
Any articles or pages created with the page builder while using php7.4 are uneditable in the back and front end. When you select them you just get a blank screen.
Exactly the same when you try to create a new article or page.
The only way to use SP3 is to roll back to php7.4 which is fine for the next month, but no longer than that.
Ian, thank you for the link, about SP4, it doesn't look like that will be a solution for me then, especially as php8 is mentioned in that thread too!
And I should also mention everything else is up to date, and I have cleared the host, site and browser cache and tried switching browsers.
Would love any other suggestions please?