It's rare to find a later medieval charter jointly issued by the King and the Queen, particularly in England. However, I've recently found some additional evidence of jointly-issued charters and want to share examples of the language used (in English translation).
Ferdinand, count of Flanders and of Hainaut, and Joan, his wife, countess of Flanders and Hainaut, to all who will view the present letters, greeting.
(charter dated 1232 -- http://epistolae.ccnmtl.columbia.edu/letter/1125.html)
We, Henry, marquis, son of late William, also marquis, and wife Adelaide, countess, daughter of late Oldric of good memory, who was called Manfred, also marquis, have professed that as spouses we both live, from our birth, under Salic law. Moreover with that mentioned spouse consenting and confirming below the offerers and donors of that church, he, constant, told those present that it was perpetual. Whoever has conferred from his property anything on holy and venerable places will receive in this world a hundred-fold according to the word of Christ. Moreover, what is better is that he will possess eternal life. Therefore we, Henry, marquis, and Adelaide, countess, spouses, give and offer and through the present charter of donation . . .
(charter dated 20 May 1043 -- http://epistolae.ccnmtl.columbia.edu/letter/1210.html)
Let it be known to all present and future that I, Baldwin, by the grace of God fourth king of the Latins of the holy city of Jerusalem, and Melisende, queen, our mother, grant and confirm the gift . . .
(charter dated 1144 - http://epistolae.ccnmtl.columbia.edu/letter/1468.html)
I've got some more and I will post more examples as I sort through them.