This has been a contentious issue since the decision was taken to move them to the Sunday in 2006.
I've uploaded the two decrees of the Catholic Bishops’ Conference of England and Wales and Congregation of Divine Worship and Discipline of the Sacraments and they can be read here.
Only Corpus Christi to crack and one could say job done!
Of course, when attempts were made to bring parity on the subject of holyday observance between the old and new calandars, the Latin Mass Society advocated with success that for a number of reasons, not least the effect on the Breviarium Romanum that this was not practical, the exchange of correspondence and the dubium submitted can be read here and here.