Pope Paul VI canonized the Forty Martyrs of England and Wales on October 25, 1970--although their Feast is celebrated in the dioceses of England and Wales on May 4 (since the year 2000) it's appropriate to remember that his action was not without controversy.
This document archived at EWTN describes some of the difficulty:
Some months before the Consistory the General Postulation, as well as the Vice-Postulation, had charged specialized agencies with following the whole national and provincial press of England and Wales, together with the European and American press, and sending it constantly everything that was published in connection with the Cause. At the same time it redoubled its efforts to obtain the widest and most accurate information not only on the attitude of English and Welsh Catholics, but above all on that of the Anglicans, with many of whose best qualified representatives there had long existed relations marked by sincere and brotherly frankness and a genuine spirit of mutual understanding and collaboration. The Hierarchy of England and Wales, in its turn, and in the first place Card. Godfrey's successor, His Eminence Card. Heenan, Vice-President of the Secretariat for the Union of Christians, made a point of establishing and maintaining exchanges of views with the competent authorities of the various Christian denominations in their country.
On the basis of this huge mass of material, it was established beyond al] shadow of doubt that at least 85 per cent of what had been printed in England and Wales, both on the Catholic and the non-Catholic side, far from being unfavourable to the Cause, was clearly in favour of it or at least showed great understanding for the opportuneness of the canonization. This applies to publications such as "Church Times", or the "Church of England Newspaper." and the most widely read English national papers such as "The Times", "The Guardian", "The Economist", "The Spectator" "The Daily Telegraph", "The Sunday Times" and many others.
On the other hand some foreign publications—including some well-known papers of protest—raised difficulties. It was at once clear, however, that these were based on insufficient knowledge of the complicated historical situation in which the Martyrs sacrificed their lives, and, to an even greater degree, of the present ecumenical situation in England. The latter calls for at least a minimum of concrete knowledge and cannot easily be understood by those who do not take the trouble to study it thoroughly Of course, everything possible has been done, by means of press conferences and other opportune methods, to eliminate this type of misunderstanding, generally most successfully.
A serious, serene and objective study of the whole situation led to the conclusion, therefore, that besides the numerous reasons clearly in favour of the canonization of the 40 blessed Martyrs, there were no real ecumenical objections to it, on the contrary the canonization offered considerable advantages also from the genuinely ecumenical point of view.
It was precisely these ideas that His Holiness Paul VI expressed and explained in a masterly fashion in the address he delivered on the occasion of the Consistory on May 18th, 1970, in which he announced his intention to proceed with the solemn canonization of the 40 blessed Martyrs of England and Wales on October 25th, 1970. In this address the Holy Father, besides pointing out, with serene frankness and great charity, the ecumenical value of this Cause, also laid particular stress on the fact that we need the example of these Martyrs particularly today not only because the Christian religion is still exposed to violent persecution in various parts of the world, but also because at a time when the theories of materialism and naturalism are constantly gaining ground and threatening to destroy the spiritual heritage of our civilization, the forty Martyrs—men and women from all walks of life—who did not hesitate to sacrifice their lives in obedience to the dictates of conscience and the divine will, stand out as noble witnesses to human dignity and freedom.
This declaration of the Sovereign Pontiff was received with practically unanimous approval, which showed how right the decision had been to proceed with the canonization. His address was given a great deal of attention and certainly contributed effectively to dispelling any doubts that may still have existed in certain quarters.
The New Liturgical Movement blog links information about Masses composed in honor of four of the forty: St. Ralph Sherwin, St. Edmund Arrowsmith, St. Edmund Jennings, and St. Anne Line.