Not sure if it helps anybody (developers in particular), but just got this through from our credit card co
Changes to Card Bank Identification Numbers (BINs)
Dear Customer,
From April next year, the card schemes (Visa, Mastercard, American Express, Discover, UnionPay, and JCB) will change the Bank Identification Number (BIN) length from six to eight digits.
What is the BIN?
The BIN is the first set of digits of the sixteen-digit Personal Account Number (PAN) on a payment card. Worldpay and our partners use the BIN to identify the card scheme, card type, and country where the card was issued.
Please note that PAN lengths will stay the same when after the schemes introduce eight-digit BINs.
How this affects you
Right now, you don’t need do anything, but if you use an online shopping card or a third-party terminal provider then we recommend speaking to them to make sure they’re ready for the change.