CE marking (at least in the UK)
As far as I am aware, for imported goods that carry the CE mark, it is the importer to confirm that the CE branding is genuine. For major companies that directly import themselves, this means that if they sell something that they've imported, they could be on the hook for damage claims resulting from selling devices that fraudulently carry the CE mark.
This being the case, if you buy your cheap tat from a major retailer like a supermarket or DIY store, or direct from Amazon (i.e. not from one of their associate sellers), you probably can have some confidence that the CE branding is genuine (it's in their interest to make sure that this is the case, because they are financially liable).
If you import direct from China through Ebay or another route, then it's YOUR responsibility to make sure that the CE marking is genuine. If you don't, then it's possible that you could invalidate any house or other insurances that may apply where it is operated, and could be liable to damages if you supply the item on to someone else!
If you buy from an individual or a small seller who has imported the item and sold it through some market or other, then things are a bit more muddy, because although they are technically liable, the chances of them actually being held to account is fairly low, so they may not confirm the validity of any of the safety marks (it costs money!).
If you have information that the CE branding on any item is not correct, you should report the supplier to the relevant trading standards organisation.
So my advice would be that if you feel you have to buy cheap tat, get it from a supplier who's reputation would suffer if they did not do due diligence and check the safety marks were real.