My 4 year old DD really enjoys longer stories and we've recently read almost all of Road Dahl (not yet the witches or great glass elevator as too scary), all three Magic Faraway Tree and all three Wishing Chair. We've also read and liked Fortunately the Milk and the My naughty little sister series (though she picked up some continuity errors in that as it's more a collection of short stories, which irritated her!).
I'm trying some Dick King Smith next and I was thinking about Just William perhaps.
Any other ideas? Nothing too scary and language she can mostly understand (obviously I can explain things here and there but don't want to be doing it all the time). Preferably funny and a bit of fantasy.