Excessive commission charged to lodge cheque in AIB

I received a Bank of Ireland cheque in the post as a refund for an item I returned to the seller.

The company that I received the refund off is a Northern Ireland company, but has an account set up especially for customers south of the border.

When I went lodge the cheque to my AIB current account, I was told the commission fee was €19.00. The value of the item I returned was €960.

This commission charge seems very high. How does the charge breakdown, and how could I avoid it in future? (At the time of asking for the refund, I gave the guy my Bank Account number, sort code, bank address, IBAN and BIC numbers... so he could do a bank transfer, but instead I got the cheque -- I had originally paid for the item with a bank transfer; don't know why he used a cheque to refund me).

Any ideas welcome,
Paul.