Hello, my name is XXXXX XXXXX it is my pleasure to assist you with your question today. What are you hoping to achieve in this situation?
As the person who took the photograph, he would automatically owe the copyright over it. Had the photo been of you, then you could have argued that by not having your consent to use it (something you could have withdrawn after he refused to provide a copy as agreed), he is breaching data protection regulations. However, the issue is that this is a photo of a dog, which in law is simply considered an object and does not have a ‘personality’ as such that you can lay claim over. It is the same as having photographed a table or a chair in your house – it is just an object that you cannot prevent them from using in their work.
All you can pursue him for is the value of the image that you were promised, whatever that may be in the current market and industry. Whether you go as far as court to pursue that though is another matter, it may not actually be worth it for the amount you want from him.
Please let me know if this has answered your original question or if you need me to clarify anything else for you in relation to this? Thanks