Look on the ps4 itself, electric specs are stamped or have a very serious tag, “IF it says 100V- 220V” 
you are fine no need to worry. Many times manuals are written poorly due to a language gap or the info just isn’t transferred from the engineering/manufacturing to the marketing dept. (which is usually in charge of the writing of the paper materials) Electrical compliance, from a manufactures perspective, its a big safety issue, liabilities etc.
If the box is stamped or tagged only 100V 
but does not specifically state that it CANNOT run on 220V - I believe you are fine.
My research has told me that Sony is only stating 100V as a deterrent from purchase, because they don’t want to lose money, on units sold in other countries.
Some info I came across on another forum, I read ALL the comments of course but there are two that really stand out, one who purchased in japan and works on a ship using 220V just fine 
and one by the original poster of the same question you have, states that it is indeed working on 240V in the UK. 
If you are unsure still…hopefully someone on this forum with 1st hand empirical data can provide you with an answer you can feel comfortable with. Please come back and let us know what happens so we can all learn from your experience.
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