Update for anyone that's interested. Received a response to my letter today which is basically what I thought it would be - 'we are sorry for the inconvenience and even though we told you ( twice) that your claim would be paid you are in fact not covered. Please accept £50 as a token for your inconvenience !'
They have offered to forward my complaint to the actual insurers of the policy ( Churchills) but my contention is that this is a cop out - my parents contract is with Nationwide and it is them they paid the premiums to and their staff who gave us the information that our claim was valid.
I intend to take this all the way to the FSA.
Anyone with suggestions on next steps? I will reply to the letter refusing the £50, should I let them pass it on to Churchill? I also want a transcript of the conversation I had with the first adviser who said we were covered. They tried to tell me that they don't keep records of all phone calls but I think this is a con - I think they keep records of all conversations for a limited period for instances such as this.
My thoughts are to refuse the £50, let them pass the complaint on to Churchill who I think will stick to the policy documentation (as they have not been directly involved) and then ask Nationwide if that is their final offer before I go to FSA