The Northern Great Dane Club are committed to ensuring the health and welfare of the breed and therefore recommend that potential puppy buyers seek out breeders that are affiliated with one of the 9 UK breed clubs and adhere to the respective club code of ethics.
You can find a list of litters from Royal Kennel Club approved breeders here https://www.royalkennelclub.com/search/find-a-puppy
Rescue
Please also consider whether you can give a home to an older dane through one of the many Great Dane rescue sites that operate in the UK
Daneline International: https://www.daneline.co.uk/
National Great Dane Rescue: https://ngdr.co.uk/