I got offered a reduced rate for a limited period (to get me into exercising) by a scheme ran by my local PCT & Council.
Called Active Lifestyle I believe it is available in many areas
From the councils web site:
Active Lifestyle
Get active.... Get healthy.... Get fit!
Active lifestyle provides a wide-range of high quality exercise and activity programmes in a friendly environment to suit all needs.
***Comprehensive lifestyle assessment and exercise programme advice
***Fully qualified instructors - to support and guide you to achieve your healthy active lifestyle
***1-2-1 Personal Training - motivate and inspire you to achieve your personal health and fitness goals
***State of the art gyms - with audio-visual technology and air conditioning to compliment a wide-range of cardiovascular and resistance equipment for new and experienced users
***Extensive group exercise programmes - to work out, chill out, relax or revive
***Low impact exercise options - including aquafit and swimming
***Exercise Referral programmes - for people with medical conditions requiring specialist exercise support and guidance
***Personal Fitness Hosts - for specialist treatment and guidance
***Free Physical activity clinics - for specialist advice to help you achieve an active lifestyle
***Health and Fitness MOTs - a range of assessments to monitor your progress and keep you motivated
I would suggest you search your Councils web site or ask at your GP surgery
Hope this helps