In most cases there isn't a clear set of pre-requisits. But indeed an acceptable level of English is definitely something you want to have. But don't worry. There is no need to have University level to be able to perform Shakespeare plays.
But best to check with the ANSP where you want to apply
ENAV
You also have the possibility to try with Eurocontrol if you don't mind moving abroad;
ATCO Eurocontrol
Good luck!