A 240V NEMA 6-15 was the preferred option in the kitchen to power my 3 kW kettle.
I would really think that the NEMA 6-15 is the clear choice for several reasons:
* Absolutely no question of code/listing issues from using non-UL/unapproved devices.
* Easy availability for replacements, fits standard U.S. boxes, uses normal faceplates in similar styles to those used elsewhere in the house.
* Easy to buy an NEMA 6-15 plug when needed, whereas if you run out of BS1363 plugs you're not going to be able to pick one up at the local convenience store.
* If you have a group of equipment that you really want retain BS1363 plugs on, you can just use a U.K. power strip and fit a 6-15 plug on the end of the cord.
