I've never had a fake from Amazon but I don't fully trust them for the reason you state (all the stock which is apparently the same gets mixed up). Argos only have their own stock, I'd be very surprised if you got a fake from there.

I've not bought a Kingston in years*, apparently they use spare capacity on other manufacturer's lines so you don't know exactly what you're getting (this is not to say they are bad, but the quality can vary considerably).

• I had some experiences with them corrupting when being used in a Pi, I changed a number of things - one being the card brand - and haven't had any issues since. The Pi is will known for being rough on SD cards so if it's going into a phone you are unlikely to have problems of this nature anyway.