Hi
The books I have found useful for finding info. on theorists for NVQ4 are:-
How Children learn by Linda Pound ISBN 1-904575-09-9
How to observe children by Sheila Riddall-Leech ISBN 978-0-435401-86-3
Child Development by Carolyn Meggitt ISBN 978-0-435420-48-2
I'm sure these books will help you with other units in your NVQ as well.
Hope this helps