Using pop-up shops as a front for grift of some kind is as old as the hills. In the 90s/00s it was tanning salons, then hand car washes in the 00s/10s. Nail bars, vape shops and those weird places with the feet-eating fish should probably also get (dis)honourable mentions.

Many UK public services are in real need of meaningful investment, but to connect that to this phenomenon without any kind of evidence is incredibly tenuous.