Each case needs to be resolved on its merits.
In new-south-wales, they were in Taylor Construction Group Pty Ltd v Strata Plan 92888 t/as The Owners Strata Plan 92888  NSWSC 1315 but that turned on the facts of the case. Other building owners might lose on the facts of their particular case.
In the above case, the owner's successfully argued that the product as installed failed to comply with the Building Code of Australia by creating an "undue risk" of fire spread and that the builder and developer, therefore, breached their statutory warranty under the Home Building Act. Importantly:
Her Honour found that a multi-factorial approach is to be taken when considering the risk assessment of fire spread (such as the extent of the use of materials, their relationship to other parts of the building such as windows and balconies, as well as their combustibility, ignitability and rate of flame spread) and one cannot look at sole factors in isolation (or be too literal or narrow when construing the term).
The same product installed in a different way on a different building might not create an undue risk - each building owner would have to prove in their case that it did.
In addition, older buildings do not have the benefit of the statutory warranty - it only runs for 3 years (since extended to 10 years). Potentially combustible cladding has been in use worldwide for several decades.
A building that did not have the benefit of a statutory (or contractual warranty) would have to prove negligence. This could be difficult if the builder supplied the product specified by the architect or engineer - the builder has probably not been negligent. The architect/engineer has no contractual relationship with the owner so they would also have to be proved negligent and proved that they owed future owners a duty of care - that is something the courts have been traditionally reluctant to do.
Notwithstanding, given the current state of the law, and the knowledge at the time it is possible that builders/architects/engineers have been negligent but it is equally possible that they have discharged their duty of care satisfactorily even though the practical outcome is less than satisfactory.
So why are they apparently not in any way liable under UK civil law, for manufacture of potentially dangerous products?
People make dynamite, automobiles and drugs - all potentially dangerous products. Indeed the UK has a thriving export market in military ordinance and that is definitively a dangerous product; the entire purpose of weapons systems is to kill or maim people.
It's not enough that something is potentially dangerous. The manufacturers will doubtless say that the product is entirely safe if used properly, and they're right. The specifiers will say that the manufacturers should have done a better job of explaining how to use it correctly, no doubt they're right too. The installers will say that neither party told them how to use the product safely, they're probably right too.
And this is why we have the problem.
Why can leaseholders and freeholders apparently not litigate in UK law for the cost of remedy, leaving the political question as "should the govt pay" and people unable to easily sell their homes?
All they have to do is find £500,000 to fund the case and hope they win. Lawyers and experts to prepare reports and testify don't work for free. Of course, if they lose then they have to pay the other side's costs too.
The legal solutions are straightforward. They're just not very attractive.
So, a lot of people are asking not "Who f#@ked up my home?" but "Who was responsible for enforcing the regulations put in place so that people couldn't f#@k up my home?"
Well, that would be governments who, for the last 40-years or so have been damndest to get out of the business of government. I can't speak for the united-kingdom but in australia, building regulation and compliance used to be a core responsibility of government, now we have private certifiers, paid for by the developer or builder, who rely on self-certification by the trades that install stuff.
Owners understandably believe that they will have better outcomes by pursuing a political rather than legal fix.
Also would it matter in law, if any of these knew of the risk before use, or only after deployment of the products?
Yes, it does matter. Actual knowledge in advance that your acts or omissions can harm others would make your actions negligent at best and reckless at worst. However, if you didn't know, then the plaintiff must prove that a reasonable person in your position should have known.
Is some kind of strict liability regardless of actual knowledge, in place, for materials sold as these were?