I wish I had an easy answer for you.
Customs can confiscate counterfeit merchandise, no doubt about it. But that is not the ONLY merchandise that can be confiscated.
One of two things probably happened here. Either it was a mistake - and they CAN happen. Or, the cell phones violated some other import law. Sometimes, some countries disallow the importation of certain goods to protect their own industries. Or, these particular cell phones may be known to have a safety issue. Or any one of a million other things.
Did you get a letter explaining WHY the merchandise was confiscated? I'm not sure about the UK, but in the US when merchandise is confiscated they will always tell you WHY and specify what law was violated. They also explain how to file an appeal should you wish to do so. I would imagine the UK has something similar...
My best guess, which is a total shot in the dark, is that maybe a customs agent thought they were branded if they looked similar to a product they regularly see? But again, this is just a guess.
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