https://www.theguardian.com/money/2022/aug/09/how-to-get-your-own-book-published-a-step-by-step-guide

Allow a budget of £4,000 to do-it-yourself, from the editing and design through to marketing

“A top-of-her-game literary agent tells us she receives about 3,000 submissions a year,” says Joe Sedgwick, the head of writing services at The Literary Consultancy. “Of those, she requests to see the full manuscripts of about 70. Of those writers, she will take on maybe five to 10.”