My solution was simply to fit it with the 4 Mbit version, but unfortunately the console reads the chip ID as part of its "security" checks, and if it does not receive the ID for a 1 Mbit chip it ceases communications.
I have been able to source the chip in an alternative UDFN-8 package, so a little work was required to tweak the PCB to accept the new part. This also means that I now have to program the security register with the chip fitted, again no big deal.
|The new PCB|
|Vs the old PCB|