The land of I don't know where

My mother used to sing this to us, but no-one I know has ever heard of it. Does anyone else known it? (And the correct tune?)

"There's a land unknown to the wise men's books
And it's never been seen by the men from Cook's.
Children go to this unknown clime
When they've been to a party or a pantomime.
They just fall asleep and fly off in their dreams
To the land where the trees grow chocolate creams
And there's no-one surprised at these wonderful things
Because they're ruled by a golliwog king.
Where is the land of I don't know where?
Sleep is the driver who'll take you there.
You just climb in his cart
And away you start
And he won't ask much for the fare.
And when you get to the land of I don't know where
Don't be surprised at the wonders there.
A blue moon on high
And pigs that can fly
Where? - I don't know where."

There's a 2nd verse as well, but I reckon that's enough to be going on with! I'd be grateful for any help identifying this.

Thanks, Carole (London)