An update on this: they just replied. They 'need more information in order to complete the investigation ... which may include payment. If payment is due, where your bank is located will determine the type of payment that is sent'. They're specifically asking for my bank details and nothing else.

This suggests to me that they're partially playing ball, although they don't mention my mention of the UK's version of EC261. I'm not sure what case information they would need given that they have the booking reference and I made the series of events clear. Any ideas? This may be better in the AA forum at this point? Or is this really just a 'we'll pay you, so send your bank details' email? I presumably should specify that the amount I expect is £520/person (unless they won't pay that for a child and a lap infant?).

One other question: they are asking for itemised receipts. We will have these for taxis, of course, but not for anything else. I had expected this, but I would add that at no point did AA actually mention them in the course of events, so perhaps worth mentioning that to them? My actual expenses beyond the taxis were £42.97, which seems pretty reasonable.

Thanks in advance...