If it is 1-3 years per count, I'm pretty sure there were 52 counts. I'm not sure if the I think 10 more he pled guilty to count in that estimate but pretty good chance he would go away for life at that point. Bare minimum, if he gets a lighter sentence with plea deal, still looking at a pretty long time. Maybe plea gives him minimum sentence and he gets 52-62 years. Thats a pretty long time. If they are treated anything like in US jail, he isn't going to survive that long.
Just a head's up regarding UK law. He won't be sentenced for life. Under current legislature the only way you get a life sentence is through murder which attracts a maximum of 38 years. However with good behaviour and of course parol, more than half of that sentence can be reduced, but it depends on the original sentencing. Some one could have been charged with multiple crimes, but it's important to understand that the biggest sentence is reserved for Murder. The sentence can never exceed 38 years, but there is an exception to this, depending on severity of the crimes committed, but it is very rarely used. I think the last time it was used was more than 25 years ago, and is called At His Majesty's service ((current) only the king can pardon him and allow him him / her to be released, basically and fundamentally this sentence gives the judge the right to sentence someone to prison for the rest of their lives without parole or early release,if the person is considered far too dangerous to the public. You cannot be sentenced because of public interest that would be unlawful.
In this case those 50 charges he admitted to, will have been or will be reduced, especially if they are of the same type of crime. Whether he broken the law previously, they will have got a probation report on the state of his mental health from a pyschiatrist. They have to take into account any mitigating circumstances and all of what goes with that, only then can sentencing occur.
This type of crime would have been originally aired at a crown court, the highest court of the land, it can take a very long time more than several years for the case to fully aired. That is, all of the documentation from the crown prosecution service (CPS), defence, probation, pyschiatrist reports, the original charges, the list will go on. In the mean time he will be held in prison waiting for a court date. That depends on how busy the courts are in London, which I was say would be very busy. Meaning a fairly long wait time before he gets taken back to court to receive his sentencing. In the first instance they have to prove it was him that committed these crimes which shouldn't be difficult.
Regardless of all of this, sentencing can take from a week to more than a year depending on it's complexity. I have no idea when that article in the Independant newspaper was written, but this case sounds fairly standard for the crimes he committed, and i'd say no more than 7 or 8 years maximum (2 or 3 years served, minus the time spent in prison awaiting his trial / sentencing and good behaviour, which would reduce the sentence further), however, he would probably have to report to his nearest police station once a day or once a week, he would be listed on the sex offenders list, which allows the community to know a sex offender is living in their vicinity. There would be other stuff that they could require of him.
At this point it is difficult to know how the judge would be thinking and more importantly what the law says exactly, since these are relatively new laws that where passed by the previous government for these sorts of online predatory abuse crimes. As for this news story not having a follow up, makes sense if the trial / sentencing hasn't even taken place yet, there is little they can say on the matter. When he has had his trial / sentencing, it will become public knowledge, but the judge may well prevent the newspapers from reporting on it any longer.