Looks like you've acquired your avatar's grip of all things football, then! You could, of course, if you really wanted to fail, go with a squad of 17 - but if you want to name your maximum squad of 25, then you will need a minimum of 8 HGPs.There is no HGP minimum, there is only a maximum of 17 non-HGP (over the age of 21). So we could have a declared squad of 17 non-HGP and not a single British player.
Seems a bit harsh on Dunk and the others, but we could.