Outside of knowing what, if any, check digits are involved in old, or new, BD numbers, it's quite possible any messing with new numbers to fit old could result in exactly that.

Given this (their faliure to inform their partners) Edna Smith et al; maybe we should send an 'IT Project Management for Dummies' to Donington Hall? I'm not a dedicated IT professional, but from what I am involved with, even I know one of the first things I need to do before implementing any upgrade, or make signifcant system changes, is to evaluate their impact on everything else......long before I start.