Greetings. You will need to turn the dial from 120 volts (US) to 230/240 volts (mainland Europe -- mainland UK). You will need to purchase an adapter for the plug to fit outlets in UK, then Bob's your uncle -- you're good to go with this hairdryer!
after some time with the travel size blow dryer... i have used it every other day, but i have notice that if your hair is still fully wet it takes awhile for it to dry your hair, but i usually walk around, or go put clothes on or even put makeup on then come back, it takes less time. as for traveling to the UK it is small and compact, as for using it in the UK, I really don't know too much about the voltage in the US compared to the UK, to be on the safe side I would get a universal/international travel voltage converter (they might have a list of countries where you can use it also) amazon have it as low as $3.23 and up. i hope this helps.
it says you can, but I am not an expert just a person who has purchased this. I also purchased the adapter and expect to use it for European travel which would include the UK. If I have any problems, I'll post.