Prior to the 1980s/early 90s there was no such thing as a "European standard voltage". 220 V derived from a 220/380 3-phase system was certainly the most common voltage but not because of any international standardisation efforts.
The earliest electricity supplies were DC and very local. Their supply voltage was typically a multiple of an arc lamp's operating voltage, i.e. 50-60 V and many DC supplies were 3-wire Edison systems. Post-1900 developments usually used AC of varying frequency, sometimes 25 Hz, I've seen a 48 Hz motor in a smallish town in Austria, 50 Hz, etc. These new networks, especially after WWI, were commonly 220/380 V on most of the continent. However, the old DC supplies, often at 220/440 V, remained in service until well after WWII. I recently looked it up for Vienna, Austria - there the last domestic DC supply was converted to AC in 1965!
Since 3-phase AC with neutral requires four conductors instead of the three for an Edison DC supply, electricity suppliers found various ways of converting those networks without upgrading the wiring, either by turning it into split-phase 110/220 V AC or 127/220 V 3-phase without a neutral. These systems remained in use for a long time, some still are - Belgium has extended 133/230 V networks and so does Norway. Both countries are gradually moving towards 230/400 V though. Of course there were also some oddball AC supplies, small parts of Italy and Austria had 150 V AC at one point. Radios from the 1950s and earlier usually had voltage settings for 110, 127, 150, 220 and 240 V.
By the 1970s, 220 V had become the de-facto standard voltage for domestic single-phase supplies across the continent, with only the UK at 240 V. In the 1980s and early 1990s that was standardised to 230/400 V across Europe (not only the EU). Actual supply voltage may vary considerably as long as it stays within 230 V +/- 10%.