I live in Westminster, quite close to Hyde Park and I definitely think that the other main parks are nicer. Smaller but also less crowded and with a better atmosphere. Try St. James Park or Green Park instead! Also, while the summer is nice, I recommend the early autumn more. And if you like friendly squirrels.. I d definitely recommend St James the most. They get (a little) less attention and often walk right up to you, even if you don’t have food (especially in times of the year when it’s not so crowded).