USB Cord Charging in UK

Do I have to take the "cube" with me from the US to the UK, or may I just plug the USB C cord into a travel plug adapter. The adapter is not a voltage converter--just a plug adapter. The Apple "cube" is dual voltage, but I'm trying to not take the "cube" and only use a plug adapter that has several USB slots with a UK plug, but does NOT convert voltage. I keep reading that the "cube" is dual voltage, but I'm wondering if the phone/iPad themselves are dual voltage and can be plugged into the UK adapter. Thank you.