What is the nicest way of putting the following across?

We thank you for the efforts you have put in making the designs mockups for us but unfortunately for one reason or another did not workout. We no longer wish to avail your services. If you feel we are eligible for some sort of partial refund for the advance we have paid, please arrange to have the money refunded the money back to our office.

Thank you.

I feel the above text is too straight and in your face. Can anybody suggest how to tone it down?