I think you will find that if you did not declare everything[ down to a pimple on your bum these days] when you took the policy out then they will refect your claim.
I have also found that the more you declare [ I am taking a disabled asthmatic lady to the States] to them the more the price goes up and we have had quotes as high as �435 for 8 days in the US for her, whereas last year it was �67 done by Thomas Cook this year they said no, not any more, go to specialist insurance.
There must be an ombudsman for travel insurance claims, and whilst you have my heartfelt sympathy, I dont think you will win.
It all depends on the information you gave them when you took out the policy and the small print says if you omit anything its null & void.
good luck and let us all know how you get on pls.