230V is the nominal voltage across the UK and EU. It used to be 240V in the UK and 220V across the EU until it was harmonised (the official term for it) in 2003. 230V is used in the electrical industry for design purposes, though 240V is still well within the allowable voltage tolerance (+6% to -10%). In practice, due to financial & pragmatic reasons, the generating & transmission voltages remained the same post-2003 in both EU & UK. Depending how far away you are from the local sub-station, and how far you measure down a skinny bit of cable, and what sort of load is being drawn, you'll likely see single phase voltages from 215V to 245V.