Maybe the PE company had seen the writing on the wall for that retail model, and extracted it's investment making failure the banks problem and no its.
I think if I were a Carphone Warehouse retail employee, I'd start getting worried about when the network starts on them, prior to moving to an internet only model, with a few flagship stores.
Other news suggests that might well be Apple and Samsung stores.
Mind you, at one time Electricity, Gas and Telephones all sold direct to the customer, and now, pretty much don't. So maybe Dixons and Carphone merging was the really smart move.