I think the 2-4-1 will probably go back to the BAEC account it came from (I don't think the link between Amex and BAEC is as strong as the wording suggests), but the taxes/fees/charges refund might end up in limbo at Amex, and need a phone call to be credited to a different account / refunded by cheque, BACS or whatever.
Can you still see your wife's closed Amex account at americanexpress.co.uk ?