Does anyone know the law on this?

Basically I work in an office of three people(me and another full-time, the other working mornings only) and the other full-time person has today announced she'll be on leave the entire month of August.

Now there's a general rule where I work that I'm asked not to take leave when the other full-time person is on leave but August is the only month when my band's drummer is not working as a teacher and, thus as a result, the only month we can really do any touring. So basically I'm determined to do this regardless of what my work say.

But just in case they kick up a fuss I'm interested to know do my work have any legal right to stop me taking annual leave at a given time?