[One (M7) Q&A, Help & Troubleshooting] stovie_steve:
Good morning mate!

It is done! I have successfully gone back to s-on and everything seems fine after several reboots and several factory resets!

These are the following steps I made:

1. I was running stock 3.62.206.1 with hboot 1.55 and S-ON, LOCKED, ***TAMPERED***

2. I ran rumrunner 3.62.401.1 which successfully S-OFF'd by device

3. I reset the ***TAMPERED*** flag and locked the bootloader using the following commands from these posts http://xdaforums.com/showthread.php?t=2470340 and http://xdaforums.com/showthread.php?t=2477792 (credit to scotty1223)

4. After this I downgraded by hboot to 1.44 from sneakyghost http://d-h.st/qfc:

- First thing I did was change my CID to HTC__032 (you will see why in a minute)

- This hboot is flashed by placing the download into the adb folder and rebooting into bootloader.

- The android-info.txt file needs modified by clicking into the file (not extracting it) and changing the model ID to whatever your model is

- Then run the command fasboot oem rebootRUU following by fastboot flash zip orig_hboot_1.44.0000_M7_RUUmode.zip

- It should say successful. If so, type fastboot reboot-bootloader and check the CID and hboot. Note you are still S-OFF

5. I then downloaded RUU_M7_UL_JB_50_HTC_Europe_1.28.401.7_Radio_4A.13.3231.27_10.31.1131.05_release_310878_signed from thanks to crushalot, http://d-h.st/Gt8. This reset the phone back to complete stock, but not stock for my original CID

6. Reboot into bootloader and fastboot oem writecid O2___001 followed by fastboot oem writesecureflag 3. This will return to S-ON but it will be reobtained again in a few minutes :) ****NOTE I DID THIS STEP TO S-ON BUT IT MIGHT NOT BE NECESSARY****

7. Download the HTC One Toolkit from Hasoon2000

8. Download, push and flash revone using the commands on the toolkit

9. Unlock the bootloader - adb reboot bootloader to check it is unlocked

10. Download M7 CWM Nandroid Backup CID O2__102 1.27.206.1 2013-03-30 from crushalot's page on XDA

11. Extract the file to the PC until you have a folder with a date on it and time (2013-03-11.17.58.27)

12. Make a new folder in your HTC one called clockworkmod. Inside here place a new folder called backup (all lower case). Place the backup here

13. Also, download http://xdaforums.com/showthread.php?t=2200628 and place onto your SD Card. Once you flash the nandroid backup, go ahead and flash this. It will fix the missing preload apps (calculator, flashlight etc)

14. Going back to Hasoon's toolkit, I copy a recovery image of CWM Recovery into the adb folder. Unlock the bootloader using Revone

15. Reboot to bootloader

16. Fastboot boot CWMTG.img - This will boot into the recovery without installing it. Restore the nandroid backup and install the preload fix. Reboot

17. Once booted up, lock the bootloader using Revone and remove tampered

18. Check for OTA - The one I got was for 2.24.206.1

- Because the stock recovery is not O2 stock recovery, once the OTA tried to install the blue bar stops about a quarter of the way as if it has frozen. Hold down VOLDOWN+POWER until the screen goes off and release. It will reboot back to recovery and continue with the installation. This will need to be done again when the screen goes black (you will see the soft keys working)

19. Allow the phone to boot up and verify the software has updated

20. Reboot into bootloader again

21. Verify that the bootloader is LOCKED, not ***TAMPERED*** and hboot is 1.54 with the OS confirming your firmware

22. Fastboot oem writesecureflag 3

23. Enjoy complete stock and continue with the OTA's

I was thinking of posting it above as a guide to other O2 UK customers to get back to stock. It seems a bit longwinded but it worked for me lol. Any steps you feel are unnecessary?