ah, now I have to show my ignorance! I can chroot /mnt/initfs but dont know how to try to mount mmcblk0p2 while there.

I've tried sfdisk -uM and that has the same results. Tomorrow I will boot up my gentoo PC and try partitioning and formatiing on there.

Many thanks for your help. it is much appreciated. Good luck with your 8gb card. The price drop was what prompted getting a new card myself.

Andy.