hi there, Dairmuid Gavin has a really good book that focuses on garden design - you can get it pretty cheaply on the Book People.
You need to decide what you want out of your garden first, seems obvious, but is entertaining important, seating, scent, tranquility, childrens play area, wildlife etc - so many decisions !
Have fun - the designing stage is so exciting, all those possibilities. You can always plant your bulbs whilst you decide what to do. Don't forget to post some pictures.