This article is from the Aerobics Fitness FAQ, by firstname.lastname@example.org (Robles) with numerous contributions by others.
Central YMCA publishes "The English YMCA Guide to Exercise to
Music" by Lesley Mowbray and Rodney Cullum, Pelham Books, ISBN
0-7207-2021-4. This is getting a little out of date now, but is an
acceptable basic text at a price of UKP 10.99
You could also try "A reference manual for teachers of Dance
Exercise" by Jill May, W. Foulsham and Co., ISBN 0-572-01472-4 at
UKP (about) 10. This is aimed more at practising teachers rather
than those in training.