Some useful sites for information – from funding opportunities to how to put together a budget:
https://producergathering.com/
https://housetheatre.org.uk/resources/
https://jerwoodarts.org/our-funding/
https://www.artscouncil.org.uk/
https://www.peggyramsayfoundation.org/grant-applications.html
https://www.arvon.org/writing-courses/courses-retreats/eats/
https://rachel.we-are-low-profile.com/blog/category/funding-faq/
https://takeart.org/artist-support/support-for-theatre-and-spoken-word-artists