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I loved the ballet class taster with Phoebe Appleby and I have already signed up for the ballet beginners course. Unfortunately didn't feel the street dance taster was suitable for beginners.
I got one of the vouchers that gave you 3 classes at Sadler's Wells - all were in different venues (Westminster Academy, Finsbury Town Hall, and Lillian Bayliss Studio) in and around the Angel/Clerkenwell area with different instructors. The ballet taster was really good, giving a good overall feel of what doing ballet would encompass, the Urban Street Dance gave you a good idea of what classes would be like as well. Bollywood was taken by a fill-in teacher the week I went - I found the teacher good but can't comment on what doing a course of classes would be like. I didn't decide to go ahead with a term of any of these - I preferred Zumba (I also attended 2 classes of Zumba at City on a different deal, with two different instructors - one I preferred over the other) but that's just my own personal taste (prefer to be constantly moving rather than stopping & starting). Overall I'd say City Academy provides a variety of different classes of good quality & value - it's just up to you what you're after.