Thanks for the tips here - I've had a go, but unfortunately I'm not having much luck. It appears I'm unable to get into fastboot any more - holding volume down during power on appears to do nothing.
I tried adb shell, but it reports "insufficient permissions for device". Also, as mentioned previously, I can only see mmcblk0 and mmcblk0p1 when using the twrp file manager, so don't know if the adb command on the thread you reference is any use to me.
I'll keep trying. Any more tips welcome!
It sounds like I'm in the same boat.
Can't get into fastboot, just goes directly to TWRP 2.6.3.0 and prompts for password.
Can't wipe /data as it give the error "unable to format to remove encryption" which is preceded by "Unable to find partition size for '/misc' and again for '/staging', '/data', '/boot' and '/recovery'.
I'm unable to use the dd command suggested as the /dev/block directory contains only 2 mmcblk files: mmcblk0 and mmcblk0p1. So, I don't have an mmcblk0p4 to write to. TWRP is running though, so I guess I should be able to access it's device and overwrite it with dd.
When I boot without the external sdcard, I have no devices other than loop0..loop7 in the /dev/block folder. Where are the partitions? I wonder if I should I be trying to overwrite the bootloader as it's ignoring my VOL-Down and just going directly into TWRP? If so, how would I do that with adb? I can transfer files and adb seems to be okay.
So, confused. Any help would be greatly appreciated.
NEW INFO
I cant get to fastboot using adb reboot-bootloader. I can flash with fastboot -i 0x0B05 flash recovery twrp.blob and it finishes on the command line but no blue line appears on the device and it just hangs there.