In the detail lies the cunning, which your post has surely helped me with.

Being the seller we're required to register for MP and also accept bank transfers from eBay/Ayden, as apposed to accepting a bank transfer from customer.

The closest eBay managed payments will come to allowing a bank transfer from a buyer is permitting purchase using a debit card, which in short is :

A debit card (also known as a bank card, plastic card or check card) is a plastic payment card that can be used instead of cash when making purchases. It is similar to a credit card, but unlike a credit card, the money is immediately transferred directly from the cardholder's bank account to pay for the transaction.