WGGB agreements cover minimum fees as well as working practices, and include repeat fees, credits, copyright, payment, working with writers, and much more.
https://writersguild.org.uk/rates-agreements/
https://editor.wix.com/html/editor/web/renderer/edit/06382022-a08c-45ef-b9e1-6fdf14ddee79?metaSiteId=996e0167-2009-46a9-8ffa-4e8af7db952b