Disabled coaching - discrimination?

I've been disabled for a long time now with scleroderma, fibromyalgia and chronic pelvic pain.  I use a mobility scooter to get around as standing or walking for too long at a time makes me very sore.  I also happen to be a high performance coach for trampolining. For the last 3 years I have applied to be a Scotland coach at the gb regional finals and each time I have been turned down in favour of anyone less qualified than me.  I was told this year by someone on the selection committee that if they picked me questioned would be raised as to how they could pick someone who uses a wheelchair.  Is this legal??  I'm pretty sure it isn't but I don't know where to go for help.  I did speak to my mp whp wrpte to scottish gymnastics asking why i wasnt chosen but ahe hasnt heard anythimg back amd that was July.  Any advice would be great. 
Thanks so much