Tendon Changing Chi Kung is fantastic. Legend has it that it comes from Bodhidharma and was passed on to the Shaolin. The traditional forms can take half a day to complete. One of my teachers, Danny Lai, has synthesized some into a few different 20 - 30 minute sets. More info and a video, here:
http://www.damazen.com/pages/chikung.html
In coming months, there'll be a few movements you can download, study and practice for free on the web site.
The practice, along with the kung fu, stretching and meditation, really turns back the clock on the aches and pains. It really works. Good luck finding a teacher in London. I'm afraid I don't know of any.
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