Requiescat in Pace Elizabeth Regina
We join with our fellows in the UK in honouring the life and passing of Her Majesty Elizabeth II.
O Lord our Heavenly Father, Almighty and Everlasting God, by whom kings reign and princes decree justice: We remember before thee the late Sovereign Lady QUEEN ELIZABETH, for the example she set of unwearied devotion to duty; for her steadfast courage; and for the love and loyalty borne to her by a great family of peoples in all parts of the world. And we beseech thee to give us grace that, having these thy mercies in remembrance, we may with one heart and one mind set forward the welfare of this land, and hasten the coming of thy kingdom of peace and goodwill among men; through Jesus Christ our Lord. Amen
The Church of England has a page for prayers and liturgical resources here.