From an ex-JW perspective , I was quite interested in the above article , which the Spectator ( presumably ) felt obligated for legal reasons to publish to allow a response to a rather unfavourable article below.
The arguments are fairly rehearsed and often used by JW "spokesmen".
(1) We are not a cult - our leader is Jesus.
(2) Previous doctrines , beliefs and practices are gently dismissed as "old light" ( to use JW parlance ) , what really matters is today.
(3) There is an emotional angle as well - the hope that the writer ( a religious professor in Chester , which must be interesting for his pupils and fellow professors , as unlike the USA it would be unusual for a Mormon to have such a position in a mainstream college ) will see his deceased father.
(4) We are basically just like another church - our beliefs may be pretty crazy ( I'm paraphrasing here ) but so are major Christian beliefs anyway . ( I have some sympathy for this standpoint - bible passages like the parting of the Red Sea , Lot having sex with his two daughters , Noah's ark , Adam & Eve etc are no less nutty or weird than some of the Mormon doctrines and churches like the Catholics are just larger cults , basically. )
The one figure I am puzzling over is his stated figure of 200K Mormons in the UK , which seems to be in line from the figure on Wikipedia. This is from 330 congregations , which would represent over 600 per congregation. This seems a lot , especially as many of those congregations have small halls , or even just meet in a village hall. Although I have known a few Mormons , I have always had the assumption that JWs are much more numerous.
I can't see the UK figures , but looking at the figures from Scotland , the 2011 Census had 4,651 declaring their religion as LDS ( which anecdotally , 1 in approx 1000 , would seem about fair ) but their own figures state 26,536 in 2009 which is a huge difference. Are they basically including pretty much everyone who has ever turned up at a meeting? Or all who are baptised ( bearing in mind that baptism is a very quick process , unlike JWs ) ? Perhaps even dead people ( in accordance with another of their unusual beliefs.) https://en.wikipedia.org/wiki/Religion_in_Scotland#Other_Protestant_denominations