What's the Name of That Book??? discussion

So I remember reading this picture book as a child and to this day it really stuck with me. It was very long and had a complex story line. It began with the main character (a mouse I think?) living in the forest until animals from the city cut down the forest killing his mother. His mother was like the forest story teller and she told him of this special island where everyone is happy. They send the mother off by floating her down a river with lots of flowers. He goes to the city where he finds these slums with lots of poor animals living in it. He then goes to the city and meets a girl animal and another future friend. This is where my memory gets blurry. I know they somehow make it into this sewer with a crocodile in it. I believe they are then put in jail until one of his friends breaks him out. They travel to the island in a hot air balloon and everyone is happy. Then the city animals come on a boat to capture them all but all the islanders band together to stop them. I really hope someone can remember this story because I remember loving both the art and story line, however, the names have alluded me. Thank you for your time!

High in the Clouds by Paul McCartney and Philip Ardagh?

Ayshe wrote: "High in the Clouds by Paul McCartney and Philip Ardagh?"

Yes that is it, thank you so much!