Hi Fanaire, it makes me angry that Insurers can treat genuine cases like yours in such a manner, it sounds like your doing all the right things to debunk their decision.
I have been through similar problems with an insurance company, i got all the experts in the field to examine me and their reports made the insurance doctors look ridiculous, eg, they had an orthopedic surgeons report based on a normal xray, so i got a report off a director of orthopedic surgery at one of our major hospitals to write out his findings based on a MRI, they soon buckled at the knees and paid up, i hope this happens to you too.
good luck
Brian