1. Plug into computer with upgraded itunes.
2. Whilst on the 'slide to upgrade screen' hold power and home button until the itunes symbol appears with the lightning cable below on the iphone screen.
3. Click restore on itunes
4. Then select update and restore.
5. After this, go through as normal and then select SET UP AS NEW IPHONE
6. DO NOT ATTEMPT TO RESTORE FROM ICLOUD BACK UP IF YOU HAVE ALREADY TRIED THIS it will not work!!
7. If you set up as new iphone you can log in on old apple account etc. The phone is as new, only my contacts saved (thank god) but it works
8. I left it at that because I would have lost all recent photos anyway due to not having backed up for along time.
9. However, you could now attempt to restore from icloud through settings in the usual way as your iphone should now be working.