The following is published on Cunard's official web site under FAQ:
Can I use my electrical appliances?
Yes you can. The voltage on board is: QM2 & QE2 – 220 volts British 3 pin sockets and 110 volt sockets Caronia – 110 volt sockets
Question to persons that have sailed the QM2 - Every electrical item (laptop, battery chargers, hair curling iron, etc) that we will be bringing on board is 110 volts; Does the QM2 have any 110 outlets? Based on the above, the outlets on the QM2 are 220 volts. I hope the above is incorrect!
I haven't been on QM2 yet (2 more weeks), but I think you're reading Cunard's answer wrong. Or at least they need to add a semicolon. I believe it reads that QE2 and QM2 have both 220 and 110 outlets. Coronia has only 110. I remember reading other posts that said there were 110 outlets on QM2. That would make sense since it spends half of its time in the US.
They should add a semicolon as follows:
The voltage on board is: QM2 & QE2 – 220 volts British 3 pin sockets and 110 volt sockets; Caronia – 110 volt sockets