Hippo, I found info on the RCCL website (see below). It looks like you will need an adapter form round to flat. I can't remember, do you use 110 volts or 220 volts in G.B.? Adapting a 220v appliance to 110 is no problem. The item won't work to full power, thus it may take longer, but it should at least work.
Now plugging a 110v into 220v is another story. I'm from the U.S. and we lived in the Philippines where they have a 220v system. We plugged a computer that was set for 110 into a 220 outlet and heard a POOOF accompanied with a puff of smoke!
I was sick. Thankfully it was only a $25 part that needed replacing. We had a saying: "There are 2 kinds of people: those who have plugged a 110 into a 220 and those who will
plug a 110 into a 220.
Q: What electrical voltage is offered onboard?
A: North American standard, 110 volts AC is used on all of our ships. Outlet adapter is required for European standard. European standard (220 volts AC, round prongs).
Stateroom outlets can accommodate appliances up to 1500 watts.