Top camp has no mains 230V electricity.
Top camp does have solar-powered car batteries, so you need to bring a 12V car-type charger for your caving light and phones.
At top camp there is one 12V socket with an expo-supplied plug providing a pair of USB sockets. Since 2 USB sockets is not enough for everyone's phones, you need to bring your own 12V-to-USB plug-in. (Providing proper permanently-wired USB charging is on our to-do list.)
USB to multiple-USB (e.g. 1:4) expander boxes don't work for charging lights. Even for charging phones they are very, very slow. So if you are using USB to charge your caving light you must bring a light charger which plugs directly into the 12V socket.
Base camp has mains power and UK-style 230V mains sockets as well as EU-style mains sockets. So your usual UK chargers will work and you don't need to bring any converter plugs.
We have one expo USB charging unit (labelled with purple gear-tape: the expo colour): it has 6 powered big USB sockets and we have 2 microUSB cables and 2 USB-C cables. People also bring their own mains-to-USB chargers but there may not be enough. So to be sure, bring your own (and label it with your gear tape).