OK, just as a data point here - had some success tonight. OTA received an email from AA. They were going to give me the refund, minus airline tax and Admin charge (£90 total!!). I questioned first the tax - I'm not going anywhere so why the tax? He said he would ask the same. Then after a short discussion he agreed to refund the full amount we paid and sent me an email to confirm that straight away. So in fairness, well done to the OTA. Payment expected in 4-5 weekdays.