Classes throughout Leeds and surrounding areas, various days and times. Lots of good information on their website.
Tai Chi & Qigong Union for Great Britain
The main body for Taijiquan in the UK, "founded in 1991 with the aim of representing every recognised style of Tai Chi Chuan, to improve and promote the art in all its aspects, health, aesthetic meditation and self defence and to provide a source of information on classes etc. for the general public."
Various info on Tai Chi from the NHS.
Info from the US Mayo Clinic