Green’s Dictionary of Slang

1. plastic.

1984

Partridge DSUE (8th edn) 897/2: plazzy bags. [...] since late 1960s.

2. in fig. use, false, second-rate.

1998		K. Sampson Awaydays 33: Them bell-ends. Been caning it down. Who are they? A few fucken rednoses. Fucken plazzy gangsters, the lot of them.
2001		K. Sampson Outlaws (ms.) 24: She hated all the roid-heads and plazzy gangsters as much as she hated druggies.