Ok so have a random half-remembered book I've been trying to find for ages! I thought it was by Enid Blyton, but have had no luck searching lists of her works:
It involved a family of children living in a big house who adopted various animals.
The first was a dog owned by another boy, who I think lived in a flat, and wasn't allowed to keep the dog. So the children from the big house agreed to look after it for him secretly in their garden. But then their parents found out and more animals kept appearing until they had an absolute menagerie.
The dog might have been a German Shepherd, and I think at one point got ill or was injured and was treated by a human doctor rather than a vet for reasons I can't remember. I can't even remember if this was a series or just one book 🤦🏻♀️.
I'd love to find it again though and would be grateful for any suggestions!