Who decides on the classification of the jobs?
The user indicates the post that needs to be filled (in other words, they supply the criteria to the temping agency who then finds someone who matches those criteria).
In practice, it can transpire that, depending on the tasks to be carried out, a driver may find themself in Category 2 with User A and, the following week, in Category 3 with User B, on different pay.
“Usually”, this is determined by the user. The temping agency can always “class” them by mission.