how to get an ombudsman letter from Apple?

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iMore Question

I was recommended by a UK Apple store manager that if I was unhappy with their decision on a warranty issue, I should take my issue to the Retail Ombudsman in the UK to resolve.
The Ombudsman said I require a letter from Apple to start the process, but the store now refuses to discuss this. I've contacted Apple Legal in Ireland, but they passed the issue back to the store.
Any ideas who in Apple can provide the letter?