Which world championship is usually held on Good Friday at the Greyhound public house in Tinsley Green, West Sussex? What is the prize for winning the tournament?

The British and World Marbles Championship. The tournament dates back to 1588 during the reign of Elizabeth I.

https://www.6things.online/2022-04-15/thebritish-and-world-marbles-championshipis-a-tournament1/

And here's a picture of the 1950 edition. As you can see in the background, it is broadcasted on radio and television to a national audience.

https://www.slaughamarchives.org/pictures/large/1724.jpg

To finish answering the question, according to the links provided above the winner gets a trophy and the title. The very first competition, in 1588, was held between two men, as the culmination of a series of contests to decide which suitor would win the hand of a local lass. The modern event has been running since 1932, with a couple of years off due to war and COVID.

https://en.wikipedia.org/wiki/British_and_World_Marbles_Championship#History