Linda Moore noted that according to Mike Parker Pearson, there are no Celts in England or Ireland. They are Gauls.
So not to be confusing, let's dispense of "Celt" altogether. It's significant that the U152's later on most probably became Gauls. This link has some excellent maps as well as the material on the Bituriges, who flourished from the 6th century BC is what is now Belgium. They are Celts, too. I'm not sure what the larger category is.
Our Proto-Gaul forefather, then, lived about 1,600 BC, about a 1,000 years before the Bituriges. But the link above references David K. Faux and his "Hypothesis C" which involves U152 and has to do with the connection of this ancestor and the Bituriges.