I think the problem with the report (as with most media stories missing out key facts), is that it doesn't detail how he became overweight in the first place. Now, I admit that I have assumed that he is overweight to start with, because he ate too much - that's pretty unfair of me, I admit.
However, the various reasons you list for him being overweight do not, in my opinion, make an valid excuse for him being overweight.
For example - medicine. I was on steroids for the best part of a year and put on four stone. Now, part of that gain was the steroids, but part of it was also that I was eating the wrong things. Just because I was hungry, didn't mean I had to eat a packet of biscuits, I could have had a healthy snack instead. I got to a point, I wasn't happy with how I looked, and how I felt, and I stopped the rot. There's not necessarily a reason he couldn't have done the same (there might be, but who knows).
Also injury/physical disability - one of my best friends has a horrendous back problem - he's seen the world's best doctors (he is fortunate to have a wealthy brother), has had numerous operations and no one has any answers. He can't work, and quite often, he can't even get out of bed. Because he can't move, he does struggle with his weight. But he doesn't make excuses. He knows how many calories he should eat a day and he sticks to it. By no means easy, but if he can do it, why couldn't this guy?
I think it was very brave of you to have this surgery and it's commendable that you paid for it yourself. But I, like Stackhead, do not believe it should be available on the NHS, except where there is a proven medical reason as to why this person gained weight in the first place.