Children's picture book, boy running away to park/garden

This is a book I've been looking for for years. It's a children's picture book I read as a kid (early to mid 90s).
It's about a boy who lives in a "standard" Brittish attached house and to get away from all hustle and bustle, when summer comes he runs off to live in a large public garden/park. Generally, he hides from there other visitors. When autumn comes he returns home.

The pictures in the book are very detailed and not at all "childlike", though the plants' sizes are some times exaggerated, giving it all a fantasy feeling. I remember some enormous lily leaves and the boy bathing/washing his clothes in a stream or pond.

Bumping up.

Bumping again.

Bump bump

Time to bump this up again.

Bumping this a last time, though I have no hopes to get any answer anymore.

Could it be Weslandia by Paul Fleischman? A young boy discovers a new plant during the summer and basically starts his own micronation?
https://www.youtube.com/watch?v=6d2XdFsnkgQ&ab_channel=mhuth4283

touchstone: Weslandia

Thanks to both of you. Unfortunately, it's not that book.