Gargoyle: thanks for the heads-up that carryon might be ok. I had to buy a new heating pad in MN and it uses way less watts than my laptop, so when I'm in business class with 110v seat plugs I know it will work. On overnights if my back gives out it would be a blessing so now I need to decide if I really need it (and the hassle of finding something to take out of my carry on bag-of-back-relief-tricks in order to make room for it and still meet UK regs.)

I've been using hot water bottles but they don't work as well and cool off too fast.