@HorseObsessed Hello, and I'm glad you decided to step out of the shadows and join the chat! 🙌 I know there is a lot of hope out there for horses, so you're not alone in that. Though if I were to recommend only one pack I would have to choose 'Seasons', as a pet (and backyard chickens) lover I personally absolutely love the content, interactions, functions, and 'cuteness' added by 'Cats & Dogs' and even more so by 'Cottage Living'. If you don't have both of these I would highly recommend them! Plus, being from England you would probably especially like Cottage Living since it's an 'English countryside'-type setting/world.
I do love my horses in other games, but there is a purpose there that at this point I don't see in this game to the same extent since it's not open world, and no 'battling' or similar actions are useful for a horse in this game. But I didn't play with a horse on Sims 3 either, so I have nothing to compare it with. Anyway, I'm sure it would be well loved if it was added in Sims 4!