I live in Cambridge and go to Greens Health and Fitness who do really good yoga classes and also there is a really good class i used to go to in Cherry Hinton (just behind the library)
Well i moved to Cambridge 3 years ago and i've joined Greens Health & Fitness and although i don't do yoga myself i've heard they do very good classes. It's a really good gym and they are all so friendly. I've been to some of the other classes that they run and they have all been brilliant