What hairstyles are allowed?

I saw that in 2024 they eased up regulations on hairstyles etc but I can’t find anything on what specific ones are allowed. What’s the maximum length etc?

Mainly asking this because I got a medium skin fade today and my parents were giving out to me saying I cut it too short and that I look like a (member of the travelling community). I have my fitness test coming up and my dad is convinced I won’t pass due to my haircut. I don’t think it’s bad at all and it just looks like a regular skin fade most lads my age would get (I’m 18). But maybe I’m wrong, any advice would be appreciated, thanks. I should point out my parents have never liked what haircut I get no matter if I have it long or short or if I grow a mullet or if I cut it all off.