Discrimination

How do you tackle discrimination that does not involve age, gender, sexuality, race, religion or disability?
Our local gym (the Peak) is offering some great discounts on membership at the moment and these are available to all apart from those on the GP exercise referral scheme. This scheme is financed by the NHS with the aim of installing healthier lifestyles and improved wellbeing in participants: the ultimate aim being to reduce future NHS care costs should such lifestyle changes not be made.

My GP referred me into the scheme 18 months ago because of my obesity and with the exercise and diet changes it has installed I have lost 7 stone with 2 stone to go till I reach my target weight. I have nothing but praise for the staff involved in the scheme; however, the same can not be said of Active Stirling who manage the Peak. They seem to regard the scheme as a cash cow and as well as getting money from the NHS they want to extract as much as possible from scheme participants. Participants on the scheme who want to obtain the discounts have to resign from the scheme and are not allowed to participate in classes associated in the scheme.
What can one do to address this discrimination?