the word "fumbling" can be replaced by serching clumsily.
"the assistant.. dos nothing to help" means that the assistant does not help customers pack their groceries.
from the phrase "the queue that's growing", we learn that more and more shoppers are waiting in the line.
the phrase "make a fuss" means protest.
the phrase "bogus shoppers" refers to women hired to check service in stores.
the word "which" refers to stores.
we learn from the extract that most british people are patient with poor service in supermarkets.
it can be inferred that the staff training program will result in improving customer service.