There are lots of amazing Pilates instructors in London. These range from fitness to rehabilitation so it depends on your needs. The best thing you can do is look at the instructors training to see the level of expertise. As there is no governing body in Pilates setting a baseline standard, qualifications can take anywhere from 2 days to 2 years. Try to find someone who has a good standard of training. However, it also comes down to personality so you may have to try a few different studios.