Image printing copyright terms & conditions

I'm starting a business that allows people to upload any image they wish and request it be printed in a particular way. I need terms and conditions drawn up to ensure that the customer has full rights to the image and claims ownership at purchase point. There are other businesses with the same model and so I know it's possible. I am unclear on what is and isn't allowed to be used ( are google images free even with water mark etc ). So I need clarity in the terms and also a disclaimer pop up to cover me perfectly. It is vital that these are bullet proof. I'm ideally looking for someone UK based as I am not sure if the law would be different here. Thank you!