The problem is that the law has no kept up with technology and the rules pretend that everything is bought via a UK importer that is satisfied with the product and resells it at their own risk.
To be honest I would prefer it is buying from places like china was only possible if your a company importing and you have to be satisfied with the product and prepared to take the rap if it kills someone. There are too many people putting their fingers in their ears because it is convenient.
I like the idea, that you are coming up with. Usually, if you buy something from a conventional distributor, in the UK, it is at least, basically safe, meets the regulations and usually works, reasonably well (but not necessarily, brilliantly).
E.g. Farnell (Element14), Digi-key, Maplins, PoundLand (UK equivalent of US $dollar stores), Amazon (where they are the seller, NOT third party sellers) etc.
Then somehow, ban/limit/control stuff coming in from abroad. I think it would have to be a much wider net, than just China. Otherwise, they might just import via other countries. E.g. China exports the dodgy/unsafe/semi-illegal items to a different country (e.g. Thailand), who then post it to the UK, to avoid a new rule, heavily restricting Chinese imports.
But the above rule(s), cause a number of practical difficulties, introducing such rules. Such as, a Chinese company, might want to send initial product samples, to someone in the UK, to consider. Which don't meet the regulations (yet), because it is an early pre-release product.
There are other major problems, with Chinese stuff. They seem to have no respect for copyright, patents, intellectual property etc. The items, can not only be complete and utter fakes. But they can be such poor quality ones, and so unsafe, that they can be serious hazard, in waiting.
As someone else mentioned, Green lasers can blind (innocent) people and/or cause disruption to aircraft and helicopters. Yet they can be (imported), relatively freely (I believe).
Unless the item, is an out and out, banned item and highly illegal. Such as real guns and explosives (which I presume are scanned for using X-ray machines and maybe other techniques). The item(s), usually pass through, probably without even receiving the appropriate customs charges (tax, VAT/duties etc).
On the one hand, I also admit I like the opportunity to buy/obtain extremely cheap but nice/interesting (often small), bits of electronic kit. Such as DDS frequency generators or meters, for a few pounds or maybe £10, rather than spending £200 .. £1000, on the proper test equipment, for doing it.
It is saddening to come across threads like this, where it has gone horribly wrong, because a poor quality or fake item, has ended up setting somewhere on fire, or electric shock hazards etc. Resulting in serious injuries or even death(s), such as in this threads main topic.
I guess this is probably like in past, many, many decades ago. When people could just buy any chemicals they like, regardless of high strong/poisonous or highly dangerous they were.
Then lots of people started to die, from being accidentally poisoned by these substances, or burn by them (acids etc) or explosions because they were incorrectly/unsafely stored etc.
Hence tough new regulations were brought in, making it illegal to sell dangerous chemicals to the general public, etc. Hence the modern law/rules system, that we live in today. E.g. Explosives can only be bought with an appropriate (highly regulated) licence, for public safety (except small/medium sized fireworks, in the UK).