On this blog I only share details of free to enter writing competitions (for several reasons, including the hope I won't be opening you up to scams). There are plenty with entry fees though - do you think those are worthwhile?
Free entry writing competitions
The Fitzcarraldo prize 'awards £4,000 to the best proposal for a book-length essay (minimum 25,000 words) by a writer resident in the UK & Ireland who has yet to secure a publishing deal.'
This is one of my favourite signposts.