If you are looking to continue your practice, you may find the following sources useful.
There are literally hundreds of great yoga books. These can be great for deepening your learning and reminding you of what you’ve learnt with your teacher. Please remember that the best way to learn is with a teacher, so that they can help you to modify poses to meet your own needs and ability, adjust you where necessary, and emphasise safe practice - so it's best to practice what you have learnt in class and are confident with, mindfully. You may also like to try Yoga Journal on-line for their home practice section.
The British Wheel of Yoga http://www.bwy.org.uk/instructor/find.htm are recognised by the Sports Council as the governing body for yoga in the UK. All British Wheel of Yoga teachers have been through thorough training. The website includes a postcode search so you can find teachers in your area. There are also BWY regional pages listing individual classes.
Iyengar Yoga in the UK http://www.iyengaryoga.org.uk/ This is a particular style of yoga (which I draw from, using props to help). Iyengar qualified teachers also go through rigorous training. This website also includes a postcode search for teachers (on the right hand side)
Yoga for healthy backs. http://www.yogaforbacks.co.uk/qualified-teachers These are specially trained teachers working with people with more severe back issues, teaching specialist classes.
Alternatively, you can try a simple Google search of ‘yoga in [insert your home town]’ but please be aware that ‘yoga teacher’ is not a protected job title – anyone can call themselves a yoga teacher, so do check out their teaching qualifications. If you have more specific health/injury concerns, you might find a yoga therapist more helpful.
Yoga Alliance started in America, and has grown in the UK in more recent years and contains teachers from a variety of backgrounds. http://www.yogaalliance.co.uk/registered-teacher.html