To factory reset go to Settings (the cog at the end of the Home menu) > System > Factory Reset. It's actually misnamed and only a partial system reset and not a complete factory reset. You are given 2 options
Keep Recordings Format Disk
With the 360 selecting Choose Keep Recordings means you won't lose your recordings or any links you've set up (but will have to sign into apps such as iPlayer, Prime, Netflix and ITV Hub again)
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