Iron Set-up - Ball position - Where on the face?

Looking down at your irons at address where does the ball sit in relation to the face?

Toe? Centre? Heel? Is there even a right and wrong place (Within reason)?

Reason for my question.

I currently set-up with the ball in the middle of the face. With my new irons, my strike point is consistently, fractionally, off centre towards the heel.

Would setting up with the ball more towards the toe help?