According to Anglicanism, is the Pope the Antichrist? In the Westminster Confession of Faith, Chapter XXV, article 6, we read:


  There is no other head of the Church but the Lord Jesus Christ. Nor can the Pope of Rome, in any sense, be head thereof; but is that Antichrist, that man of sin, and son of perdition, that exalts himself, in the Church, against Christ and all that is called God.


There is also this document which goes through the wording of several Anglican theologians, leaders, and government officials, arguing precisely that same thing (and thus arguing against any effort of collaboration). The documents states:


  If  the   English  Reformers  are   to  be  believed,   and  the  official  language  of  the  Church  of  England  for  a  couple  of  generations   at  least  after  the   Reformation  is  to  be  accepted,   the  Church   of  Rome  is  the   Apocalyptic  “Babylon   the Great ,” and  the Pope  that “Man of Sin”  delineated by the  Apostle, as one  of the  manifestations of  Anti-Christ.


Thus, is the above article of faith in effect stating that, for the Anglican church, the Pope is the Antichrist? Is this thus official doctrine?
No. 

The Article of the Westminster Confession quoted in the question clearly identifies the Pope as the Antichrist. However the Westminster Confession is not a doctrinal standard of the Anglican Churches. In the UK the Westminster Confession is the official doctrinal standard in Scotland, but not in England. The Church of Scotland, however,  is not an Anglican Church.  (There is an Anglican denomination in Scotland, the Scottish Episcopal Church, but it is not the official national Church.)  

The Westminster Confession was produced in England during the mid-seventeenth century period of the Civil Wars. It was intended to replace the 39 Articles as the doctrinal standard for the Church of England. Following the death of Cromwell and the Restoration of the Monarchy, in the person of King Charles II, the Westminster Confession was not accepted, and the 39 Articles were restored.

The 39 Articles do not mention that the Pope is the Antichrist. Article 19  state that the Church of Rome, like those of Jerusalem, Alexandria and Antioch, has erred. Article 37 affirms that the Pope has no jurisdiction in England. 

Article 35 refers to two books of homilies saying they contain a godly and wholesome doctrine and were judged to be read in churches. (At the time the Articles were finalised in 1563 many priests were not licensed to preach but only to read homilies, the reason being lack of education.) It does not imply that everything in the Homilies Books is necessarily to be regarded as an article of faith, having the same status as the Articles themselves.

The question references a document produced by the Church Association, a body formed primarily to oppose Romanising and ritualist tendencies in the Church of England and seems to have been written following the Malines Conferences between Anglican and Roman Catholic bishops in the 1920s. It identifies three references within the homilies which it says  supports the identification of the Pope with the Antichrist.  One refers to the "Romish doctrine of Justification  by human merit as the greatest arrogancy  and presumption that Antichrist could set up". The second says the Bishop of Rome ought rather to be called Antichrist than Vicar of Christ. The third that many popes have been false Christs, together with a reference to Luke 21 v8 ("many shall come in my Name").    It can be argued that the first, while stating the worst thing the Antichrist could do was what the Pope actually did do, can be argued not necessarily to imply that the Pope is the Antichrist, merely that the Antichrist could, in this particular respect, not be any worse than the Pope. The second, in saying the Pope is rather one thing than another is argued not to imply that he is necessarily either. The third by referring directly to Luke 21 seems not to be talking about the Antichrist but the many who falsely come in Christ's Name. 

So it is not clear that even in the Homilies is there anything in formal Anglican doctrine that clearly states that the Pope is the Antichrist. 

There have at times been special prayers, often to be said annually over many years, that gave thanks for delivery from Popery, but these are no longer observed. (The Anniversary of the Gunpowder Plot was for over 200 years a national holy day of thanksgiving in England.)  Nevertheless even there there seems no specific identification of the Pope and the Antichrist as one and the same person.

The Thirty-Nine Articles, many of which were originally drafted by Cranmer, were approved by Convocations in 1563 but not officially promulgated until 1571. This followed the Pope's excommunication of Elizabeth in 1570. Only in 1571 were they are-approved by the Convocations (of Canterbury and York), the Houses of Commons and Lords, and the Queen. It is thought they were somewhat reticent on the Pope as Elizabeth had no strong wish to antagonise him, at least before 1570. 

The official Anglican doctrine then is silent as to whether the Pope is the Antichrist. It was the view of most Protestants in most countries in the early generations of the Reformation and is the official doctrine of the Church of Scotland. But not in the Church of England or other Anglican Churches.

In the seventeenth century most Anglicans held that he was and in the twenty-fist the vast majority hold that he is not; but the Church has no official position on the matter.