Ok, in this case you should reflash with stock rom http://www.needrom.com/download/official-p6-rom-30-06-16/
then do the OTA-s until the last one and then
re-flash mad TWRP and then install mad rom and gapps pico again.
That's it. It takes around an hour but i think you don't have other choice.
Thank you for the kisger13. You pointed me in the right direction and I am up and working again.
The Only bit i had to add was that the TWRP recovery would not let me successfully apply the stock rom. In the end I found someone who had extracted and uploade dthe stock recovery img file and blew that back to the phone using fastboot. Then I was able to restore the stock rom and was back up and working.
From that point I re flashed with TWRP 3.02 and re-installed MAD ROM.