if you wait until you're an adult, all you need is the piece of paper itself, with your signature and those of two witnesses, stating that your former name will from now on be know as your new name, and all that.
while you're still a minor, whoever is your legal guardian will need to give permission. other minors would have to ask their parents (both). a minor's name change also has to be approved by some senior master on behalf of the master of rolls and lots of legal stuff to protect the child's best interests.
the only thing that could change your current situation, is if you have been issued a gender recognition certificate. if you have one, you can use that as evidence of your name change instead of a deed poll. but maybe you'll have to be an adult to get that too.
