You can just switch the box off with the switch on the back of box which might be easier to access than your plug, or a basic "factory reset".
It's only a partial system reset and not a complete factory reset. You are given 2 options,
Keep Recordings
Format Disk
Choosing Keep Recordings, means you won't lose your recordings and any planned recordings or series links you've set up, but you will have to sign into your apps such as iPlayer, Prime, Netflix and ITVX again, also Match frame rate and Standby power consumption will go back to their default settings if you have changed them.