Recommended reading for those wishing to understand more about yoga:-
The Heart of Yoga: Developing Personal Practice by T.K.V. Desikachar This is a great place to start to gain a deeper understanding of yogic principles and the thinking behind Viniyoga. It also has information on starting a home practice with some short practices written out. There is a translation of The Yoga Sutras- the Yoga Sutras were compiled around 400 CE by Patanjali, using material about yoga from older traditions.
Yoga for Wellness by Gary Kraftsow This book has lots of case histories on individual ailments and is a great resource for how to deal with health conditions and how to apply yoga. Easy practices with good pictures.
Links
Main UK association for Yoga
Viniyoga's UK governing body
Viniyoga teacher training and material
Individual tuition and classes with Mike Young
Global movement for health, joy and world peace