Afraid not. When our dog got hit ( thanks to the mrs being a muppet ) i asked at the local police station as to wether the driver should have come forward, as i was curious.. and apparently no there is no obligation to report hitting a dog. Only a person or a livestock animal.
Nice that your local police don't know the law.
https://www.askthe.police.uk/content/Q434.htm
Falls under the Road Traffic Act that you HAVE to inform for hitting a dog.