Only around 6 million confirmed Anglicans in the UK

If you want to measure the failure of Christianity, ask yourself how many people in total in this country have been confirmed. But confirmation is not bar to later renunciation and conversion to another faith. These days, the government thinks it perfectly acceptable for its citizenry to have second thoughts about remaining in the sex they were born as, or remaining married to their spouse once they become bored and irritated with their marriage. Today you may believe that Christ is the co-equal of the Abrahamic God, tomorrow you may well  feel like becoming a member of the opposite sex. The government encourages this and sets Ofsted on faith schools to enforce what are now called "fundamental British values" on all faith schools not disposed to accept this kind of sexual diversity.

https://www.youngcitizens.org/british-values

Imagine the progress we would enjoy if the Tudors had enshrined what would have been called Tudor values "as fundamental English values".  After the death of Elizabeth, James would have imposed these English values as British values and we would all be enjoying the fun of jousting, beheading as well as the persecution of Catholics. There would be no need to persecute Jews because they had already been expelled in 1290.

The Trinity is the Achilles heel of Christianity. Not only is a Christian required to believe in God, he is also required to believe that an executed revolutionary is the co-equal of the supreme and eternal Abrahamic God, which Jews and Muslims understandably find blasphemous and idolatrous.

After the Age of Enlightenment, no one really believed in this any more, nor were they required by law not to deny the Trinity after The Doctrine of the Trinity Act 1813.
https://en.wikipedia.org/wiki/Doctrine_of_the_Trinity_Act_1813

Christianity has failed because of its idolatry. Which important Christian would say he really believes Christ is the co-equal of the Abrahamic God unless his or her job depended on it?

As one imperialistic World War followed another imperialistic World War in the 20th century for no apparent reason and for no apparent benefit to the ordinary British people, it was not surprising that the British began to throw out the baby of Biblical morality with the bathwater of the Trinity.

If the formerly Christian West is now failing and faltering, it is possible that God is punishing those who identify as Christians for nearly 1800 years of idolatry.

https://en.wikipedia.org/wiki/Shahada

https://www.churchofengland.org/sites/default/files/2017-10/2016statisticsformission.pdf

15,900 people were confirmed in 2016, at 1,950 confirmation services.

Of those people confirmed in 2016, 59% were female. Since 2006, the annual number of confirmations has fallen from 29,380 to 15,900. There has been a slight shift towards a greater proportion of those confirmed being aged over 20, from 39% of confirmations in 2006 to 45% in 2016.

https://www.churchofengland.org/sites/default/files/2017-11/2015statisticsformission_0.pdf

16,700 people were confirmed in 2015, at over 1,800 confirmation services. 58% of those confirmed were female.

https://www.churchofengland.org/sites/default/files/2017-11/2010_11churchstatistics_0.pdf

Totals for 2010 

8,867 male
13,482 female
22,349 total 

Comparable figures for 2009:

9,799 male
15,229 female
25,025 total

Church of England loses more than 100,000 worshippers in a decade
But attendance is still strong during the festive season

http://www.churchsociety.org/issues_new/church/stats/iss_church_stats_confirmations.asp

1950  142,294
1951  139,431
1952  148,982
1953  154,548
1954  159,957
1955  162,848
1956  167,403
1957  172,288
1958  173,177
1959  182,721
1960  190,713
1961  191,042
1962  181,623
1963  169,103
1964  156,583
1965  146,031
1966  140,134
1967  135,476
1968  125,294
1969  119,150
1970  113,005
1971  109,840
1972  106,216
1973  100,227
1974   96,379
1975   95,349
1976   94,318
1977   95,969
1978   95,969
1979   95,969
1980   97,620
1981   90,300
1982   84,566
1983   81,951
1984   79,433
1985   76,934
1986   72,652
1987   65,853
1988   63,895
1989   61,656
1990   59,616
1991   55,246
1992   57,374
1993   51,784
1994   48,024
1995   43,667
1996   42,768
1997   40,881
1998   39,926
1999   37,469
2000   36,387
2001   33,400
2002   33,400
2003   31,800
2004   30,400
2005   29,800
2006   ?
2007  ?
2008  ?
2009   25,025
2010   22,349
2012   ?
2013   ?
2014   ?
2015   16,700
2016   15,900

5,688,815

https://forums.catholic.com/t/are-confirmed-catholics-in-a-database-somewhere-to-track-everyone/280331/6

Q.  Are confirmed Catholics in a “database” somewhere to track everyone?

A.  No.

Sacramental records are recorded by hand in a sacramental register in each parish. Records are signed by the priest. Records are reviewed and signed by the bishop on his visits to the parish.

No one may access those records except the pastor and his designee. The pastor may give a certificate with the parish seal to those in need of their sacramental records or send them to the pastor of another parish (for example, for a marriage). A parent may also request the sacramental records of their child.

On a periodic basis, old records are sent to the diocesan archives. The diocese archives them, ours does microfiche, but the original books are always maintained. The diocese releases archived records for historical and geneaological research on the same schedule as the US Census.

Sacramental record books for closed parishes also go to the diocese.

Yes, we do have a computer system with our parish members in it, and there are data fields for sacramental records, but a computer may NEVER be used in place of the sacramental record book and are NEVER considered the official record.

No, these records are not centralized.

Is the corrupt clergy trying to hide their failure?

How many Christians are there really, officially?

God only knows.

https://www.independent.co.uk/news/uk/home-news/church-of-england-anglican-statistics-loss-worshipers-decade-sunday-attendance-a7384631.html

https://en.wikipedia.org/wiki/Religion_in_the_United_Kingdom#Islam

Estimates in 2009 suggested a total of about 2.4 million Muslims over all the United Kingdom. According to Pew Forum on Religion and Public Life, the number of Muslims in Britain could be up to 3 million. The vast majority of Muslims in the United Kingdom live in England and Wales: of 1,591,126 Muslims recorded at the 2001 Census, 1,546,626 were living in England and Wales, where they form 3 per cent of the population; 42,557 were living in Scotland, forming 0.8 per cent of the population; and 1,943 were living in Northern Ireland. Between 2001 and 2009 the Muslim population increased roughly 10 times faster than the rest of society.

https://en.wikipedia.org/wiki/Religion_in_the_United_Kingdom#Judaism

British Jews number around 300,000 with the United Kingdom having the fifth largest Jewish community worldwide. However, this figure did not include Jews who identified 'by ethnicity only' in England and Wales or Scottish Jews who identified as Jewish by upbringing but held no current religion. A report in August 2007 by University of Manchester historian Dr Yaakov Wise stated that 75 per cent of all births in the Jewish community were to ultra-orthodox, Haredi parents, and that the increase of ultra-orthodox Jewry has led to a significant rise in the proportion of British Jews who are ultra-orthodox.

However various studies suggest that within some Jewish communities and particularly in some strictly Orthodox areas, many residents ignored the voluntary question on religion following the advice of their religious leaders resulting in a serious undercount, therefore it is impossible to give an accurate number on the total UK Jewish population. It may be even more than double the official estimates, heavily powered by the very high birth rate of orthodox families and British people who are Jewish by origin but not religion; as it currently stands, the Jewish as ethnicity section is not documented on the census.

http://corpus.quran.com/translation.jsp?chapter=8&verse=65

O Prophet, urge on the believers to fight. If there be twenty of you, patient men, they will overcome two hundred; if there be a hundred of you, they will overcome a thousand unbelievers, for they are a people who understand not.

Now God has lightened it for you, knowing that there is weakness in you. If there be a hundred of you, patient men, they will overcome two hundred; if there be of you a thousand, they will overcome two thousand by the leave of God; God is with the patient.