Most Western Europeans who have an interest in religion are returning to their indigenous religions more than anything.Celtic,Saxon and Norse 'festivals' have a much larger turnout than anything else.
As for the dwindling popularity of Christianity......Christian 'charity' is increasingly being seen as the reason for mass immigration to Western Europe(and the colonies).A number of Christian churches in my own country are currently being 'blamed' for lobbying the government to accept 10,000 refugees to get permanent residency.That being said,numbers attending church here have actually increased over the past 5 years(possibly due to large numbers of non-anglo immigrants,which kinda fits in with this news item).
A strange phenomenon is that in America Christianity is associated with the political-right but everywhere else it is seen as firmly to the left,'one-worldy',pro-immigration and anti-nationalistic.
Well you emphasized the word 'false' but that can't be a good definition of a cult. Every religion thinks every other religion is false. If that were the basis of the definition then Buddhism would be a cult to Christians and vice versa. The rest of the definition is more workable. "Living in an unconventional manner under the guidance of an authoritarian charismatic leader".
Under this definition Hare Krishnas and Branch Dividians would certainly be a cult.
Mormons, at least the ones I've known don't live in an unconventional manner. And while Joseph Smith may have been a authoritarian the current head of the Mormons is not. (Can anyone even name him. I sure can't). I don't know much about the Witnesses. Do they live strangely? Do they have a charismatic leader?
I find this a little hard to believe. Having an interest in your cultural heritage is not the same as a religion. I'm not sure you can "return" to a dead religion. There is no continuity between the actual people who practiced these religions 1000 years ago and the modern people. As most religions both the rituals and the meanings are somewhat secret and passed down verbally (in antiquity) I don't see how you could really revive them. As an example: Civil War reenactors are not fighting the civil war. Norse Religionists are more reenactors in my opinion. Do they REALLY pray to Thor with the belief and sincerity that Vikings did in 500 A.D. I am extremely sceptical.
It does speak to some sort of spiritual hunger.
That is an interesting observation that gives something to think about.
There are many missionaries in Ireland and England, however it is tough sell with the long held religious war in Ireland and the formalism of the Church of England. There are a lot of good people there who live good lives. Actually revivals are harder in that type of situation. People who are good normally don't think that there is anything wrong with them, whereas people who worship idols and have lots of sexual promiscuity and other obvious sins abounding are more open to a gospel that saves them from their sins.