Travel insurance/pre existing condition.

nco41

I had a holiday booked to take my two children and i to Egypt costing £2500.
I booked holiday Insurance through First Assistance travel insurance. I booked the insurance over the telephone a week before we were due to go(i always do this).I was asked the usual medical questions about my children and i .
The following day my mother dies suddenly and most unexpectly. Obvioiusly the children and i could not go on the holiday.I contacted the travel agents to try and postpone the holiday.I was advised that as i was leaving in under eight days i could not do this .So i would have to cancel and claim on the insurance.I was slightly miffed but i had little choice.
I contacted my insurance company who sent me out a claim form. I duly completed the form and sent it back enclosing my mothers death certificate. My mothers cause of death was listed as heart failure.On the claim form i stated that my mother has a heart attack some twenty years previously but was in excellent health.I also go my mothers GP to write a letter stating that mum had been in excellent all round health for many years and her death was not on untimely but premature.
A few weeks later i received a letter telling me my claim had been turned down due to my mothers pre existing medical condition that i had failed to disclose. I contacted First Assistance to protest as i was not taking my mother on holiday with us. They claim that i would of been asked about family members health when i took out the insurance.I maintained that i was never asked.Why would i as they were not coming on holiday with us. I mentioned if they had asked i would i told them about my Fathers health first and formost . I asked them to listen to the recorded telephone conversation i had with them when i took out the policy,but apparently they do not record every message.Convient. They claim that i would of been told of the pre-existing rule for parents as all their staff say it,but they cant prove it.
First Assist also told me i would of been advised of this rule in writing with the written policy. I explained that i had not received the written policy.
They are adament they will not pay out as i did not advise them about mum.I still maintain i was never asked ,told or advised of the pre-existing parent rule.
What can i do????
I would be greatfull for any advise.