That's not the way it works, ian. The question is not settled when you say it is, it was settled when Britain signed the European Convention on Human Rights, which, as you have already pointed out, made judicial executions an infringement of human rights. No exceptions, not even for church-goers.
As for your mini survey, its validiy is reflected in the way you describe it: minute.
I don't quite understand the purpose of the statistics you quote: I agree that there are lots of murders in the UK, far too many, and any way that number can be reduced must be tried. But it must be a legitimate way ... Otherwise we could consider bringing back torture for suspects. Rack them until they admit they did it. It worked in the good old days didn't it? Then hang them to make sure they don't do it again.
"...habitual killers cannot be rehabilitated," you say ...
What, none of them? Ever? How do you know this?
I must point out, however, that we haven't just been talking about habitual killers. We've been talking about all murderers, and most murder victims know their killers and are frequently closely related. Such killers are not serial murderers but have reacted to a situation they could not handle any other way. Those people are unlikely to kill again, and probably regret their action.
Then you ask, what about the Human Rights of the victims? Pardon me for stating the absolutely-bleeding-obvious, but they're dead. Whatever right to life they had was taken away. Unlawfully taken away, granted, but their human rights are fuck-all use to them now. The killer must face the consequences, but it affects the victim not at all whether he be imprisoned, hanged or paroled.
The victim's relatives have lost a loved one, a partner or parent or child; a bread-winner perhaps. They will naturally be grief-stricken, and they will be filled with hatred for the murderer. But their human rights are unaffected.
Justice isn't giving satisfaction to the angry and disgusted in order to mollify them, it is meting out a punishment that is appropriate in the view of sober-minded, dispassionate judges according to a law that has developed over hundreds of years and has been enacted by democratically elected representatives after serious argument and debate (on a free vote, by the way).
"If a person carries a knife or any type of weapon to carry out a robbery or any other crime, be assured that he is going to use it."
If that is true, why do many armed robberies take place where the weapons are displayed but not used?