Depends what you mean by National 11+ papers?
The herts eleven plus consortium schools examination involves two standard papers in mathematics (50 questions in 50 minutes) and verbal reasoning (100 questions in 45 minutes); answering in the booklets - some multiple choice.
Best papers to get familiar with:
ISBN 0708703798 NFER Verbal Reasoning standard (note these do not contain 100 questions, they are 80 questions in 50 minutes)
ISBN 070870381X NFER Mathematics standard
You will see these papers in the Bookshop of this website, link below:
For useful information on Herts see the other parts of this Hertforshire section as well as the subject specific sub-forums.