Good review, I am in UK and have one. It's very handy with an amazing form factor

It's not really designed to brute force charge your iPhone from empty though, it's meant to be attached to your phone when the phone is near full, and it will keep your phone topped up for a long time, it doesn't have to draw on as much power and is more efficient.

Also charging via the cable as well as being faster at 20w will give more charge than wireless where some efficiency is lost.