Default Need Stock ROM For Htc One

Hi my HTC one m7 is currently running ViperOne and I would like to go back to stock os. the only problem is I'm a bit of a noob at this and I need to know how to install it, do I need an RUU ?, also Im in the UK and the carrier is vodafone. I currently have s-off and unlocked bootloader and really need to get back to stock 4.4.2 android. Any help will be much appreciated. Thanks