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.
The solar/battery system provides various connectors:.
At top camp there is one expo-supplied 'cigarette' plug providing a pair of USB sockets. Since 2 USB sockets is not enough for everyone's phones and lights, 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) hubs don't work for charging lights or drill batteries. 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 sockets..
Base camp has mains power and UK-style 230V mains sockets as well as a few 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 USB-A 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).