In Gaul it was introduced. In fact, outside the far south it wasn't grown until the Roman period, but was imported, at great expense: according to Diodorus Siculus Gauls would exchange a slave for a single amphora of wine (26:3). Another passage about Gaulish feasts, a quote from a lost book by Posidonius (probably also the source for Diodorus) in a work on feasts by Athenaeus says that they imported their wine from Italy and the area around Massilia (Marseilles), and that the common people drank beer (korma) and honey flavoured beer.

It was a quite significant trade too: it's very difficult to estimate volumes of something this ancient, but, based on remains of particular short-lived amphora style, one author estimated that Gaul was importing something on the order of '100,000 hectolitres a year' during the first century before Christ.

Sources: Primarily 'The Celts' by Barry Cunliffe, but I also found the 'wine and the vine' book I linked in the last paragraph while researching this that looks quite good.