Thanks for bringing this to our attention, neil-drew.
At the moment, there are no similar cases reported about MBNA credit card feed downloading in reverse. For now, you can try using the CSV file to import transactions.
To learn more about importing transactions using CSV file, here's an article that you can check out: How to import bank transactions using CSV files.
While transactions are being downloaded in reverse, I recommend you get in touch with our QuickBooks Care Support for further investigation.
Here's a link on how you can reach them: https://quickbooks.intuit.com/uk/contact/.
I'm just a post away so please don't hesitate to reach back to me if you have further questions when downloading bank transactions in QuickBooks Online.