I’ve got no problem with this at all - Britain has been pagan a lot longer than it has so far been christian.
As long as children are taught about it objectively as the belief system that christianity replaced, then knowledge is a good thing.
True, but the current inhabitants haven't been. What they will be teaching is neo paganism - "new age" and "wicca" and that kind of stuff. It has to be that way because very little is definitively known about ancient british pagan beliefs. The druids didn't leave any written records of their belief systems, forms of worship and ceremonies. The only people who did were the Romans, who loathed them, and can therefore hardly be expected to be impartial observers. As long as children are taught about it objectively as the belief system that christianity replaced, then knowledge is a good thing.
And what would be the chances of that happening?