The UK uses the same voltage and frequency as most of Europe, Africa, Australia etc. i.e. 230V @ 50Hz Most mains adapters for laptops etc. are fairly tolerant of different inputs so do not be too concerned about that; just check. The problem is that UK plugs and sockets are quite different to most of the rest of the world (except Kenya for example!).
You will therefore most likely need a UK visitor mains adapter that can be bought at airports and travel shops.