Can anyone tell me how a dog or bitch gets it's stud book number?  As I understood it, it was if they got 1st in their class at a champ show, if I am right, do you have to apply for it?

No depends on the breed and what band it is in. As far as I know you get it automatically.
http://www.thekennelclub.org.uk/item/611

Check Goldmalis link, if you have won one of the qualifying classes then the KC will post your stud book number to you automatically. You then use this instead of your registration number on the crufts entry form etc

What breed are you ?
I know in Band E it is first three places but only in Limit or Open classes
Not too sure on Junior warrant though- maybe some one else can help on that one