I would install a 6-20R and a cord end and call it a day.
You may also have to get the coffee maker recertified depending on local policies. This receptacle only needs a regular permit and is legal to your system. Any attempt to install a british plug should requre a Special inspection and have the outlet recertified for use on a North American system. I would not grant said permission as the receptacle I have mentioned meets the electrical requirements of the British appliance.
CAUTION: The Euro appliance has a grounded wire and the North American 230 volts does not. there could be a hazard created by the change if the grounded circuit wire is in anyway involved with the chassis. This is not the bond (green with yellow stripe)wire I am talking about.
I think the black wire is grounded in Britan
