England is not where Easter was first kept, so the aberrant pagan root of the English word “Easter” (the words in many other languages refer to the Passover) is neither here nor there: Easter is not in any sense a continuation of pagan fertility festivals. In fact, there is little or (almost certainly) no continuation of pagan practice anywhere in these islands, and little, if anything, is known about pre-Christian religion here; most, if not all, allegations to the contrary derive from Protestant polemic against practices originating in the Middle Ages, and usually the Late Middle Ages at that. (The modern religion known as Paganism is an invention from scratch, the very earliest roots of which are in the late nineteenth century.)
The latest thinking on this can be found in the various publications over the last decade or so of the social historian Ronald Hutton, himself raised a neopagan:
The Pagan Religions of the British Isles;
The Rise and Fall of Merry England, 1400-1700;
The Stations of the Sun: the Origins of the Ritual Year in Britain; and
The Triumph of the Moon (on modern neopaganism)
About the only thing for which Hutton can establish a probable pre-Christian origin is the entirely transposable custom of lighting fires on the quarter days. But all of this passes largely uncommented on in everyday opinion; Professor Hutton should be on the BBC, with a major television series plus tie-in newspaper articles. Which is why he isn't.
As for the date of Easter, the last census found that seventy-two per cent of Britons voluntarily described ourselves as Christians; I should be most surprised if any more than one or two per cent belonged to Eastern churches, with their different liturgical calendar. The formula for calculating the date of Easter is not complicated, and has in any case already been applied in relation to years long into the future. The results of these calculations may easily be, and are, consulted by schools, businesses, the National Secular Society, or anybody else.
Of course, the NSS really wants to abolish the Easter Holiday because it is a reminder of this country’s Western Christian roots, to which the population overwhelmingly continues to adhere, which are the constitutional basis of the British State, from which derive both of our principal political traditions, and which has also contributed hugely to our third political tradition. If anything, we need an ecumenical counter-campaign to restore Whit Monday properly so called, and possibly also to make Ascension Day a public holiday, in line with Europe Catholic and Protestant, EU and non-EU.