I've received a letter this morning on this issue, from an "Executive Resolution Specialist", dated 24th November. They write at the request of the "Data Protection Office."
It contains no more information than the C&P responses from the mod team in this thread really; no reference to how/why it occured, whether my data was compromised. Just "It happened, we investigated. Soz".
It also says they've locked my account as a precaution, but that happened a while before the date on the letter.
So, still none the wiser