Oh come off it. Making amateur porn at work is gross misconduct in anyone's book
Look, as far as I know almost everyone thinks that, but getting people fired is often not straightforward.
Now, I am not in the UK, so the laws are not identical, which obviously would make a difference. It seems that here if something is done in a toilet, it's considered private. There was a case of an employee masturbating in a toilet at work a few years ago locally to me, and it went to the courts in the end, and what made them agree he could be fired is that the other employees could hear him.
What my sister said was that in reality, in all the cases she had fired people in public or semi-public employment sectors, only twice did they NOT pay the person off in the end. It's just not worth it in most cases to go through the whole process or arbitration the courts etc, especially if they can claim some kind of bigotry, mental illness or something like that.
I find that all too believable whether or not I think masturbating at work and putting it on the internet is misconduct.