- so I've decided to sell my M8, so I thought it best to get it back to stock, so I did the following :
1) flashed stock rom (from the XDA thread) to suit my CID.
2) flashed stock recovery (also from XDA) which obviously removed TWRP.
3) relocked the bootloader.
4) S-ON I never actually managed to get S-OFF so this was a non issue.