Yeah, we only know the most vague and basic stuff about druids. Which works out well for the Neo-Pagans, because it means that they’re pretty much free to make up whatever they want as parts of their “ancient traditions”.
“And then. . .ummmm. . .the next part of the ceremony involves. . .errrrr. . .involves all the women taking off all of their clothing and dancing! Yeah!”
The Phoenicians only started to really take off and go some time around 1100 BC, after the Egyptian and Hittite empires had been knocked into decline by some mysterious event (usually linked to the elusive “Sea People”). They eventually established lots of colonies in North Africa and Spain and that area, which did trade with the Britons—mainly for tin from Cornwall, if I recall correctly. The Phoenician colony of Gades (now Cadiz) in Iberia was the main group involved with the tin trade, apparently, but they were very secretive about their sources. Nobody is quite sure when they started trading with Britain. Herodotus mentions it vaguely in Book 3 of his Histories, which makes it around the mid-4th Century BC at the latest. But it wasn’t until about that same time that the Celts moved into Britain, which means that they wouldn’t have had much experience with the Phoenicians.
The Phoenicians didn’t have much to do with Gaul. Gaul was in the Greek sphere of influence, and the Greeks and the Phoenicians were careful to keep out of each other’s way (except for in Sicily, where things got complicated). The Celtic Gauls, then, were influenced more by Phocaean culture and not by Phoenician. . .which is why they’re called “Celts” in the first place, that being a Greek-derived name.
So, seeing as how Phoenician culture isn’t that influenced by Egyptian, and that Celtic culture isn’t that influenced by Phoenician, it’s not too likely that the druids were inspired by ancient Egypt.