Peterborough United 8
Or do you mean different vowels? There are only five. And none have five.
AFC doesn't count in my book, not as A or as association football club.
Player with the most letters in his name (a two part name only, for Joao Pedro Santiago Maximillian Everard Corpuschristi de Jesus' sake) that uses the fewest letters.
I'll star of with Callum McManaman
Divide the number of letters by the number of different letters for the score:
Fifteen...