Whilst they do drive for a living DPD delivery drivers are in vans, 3.5t and under in weight, they are not subject to EU driver hours regulations (which HGV class drivers are) and even if they were, on local multi drop work it's very difficult to exceed your driving hours allocation, most will have a huge number of drops but within a specific postcode area.
If the OP is in Staffordshire then today could well have gone Pete Tong for the driver due to the M6 closure between J14 and J15, the surrounding routes have been pretty gridlocked all day.
For the record the max driving allowed is 4.5hours (continuous or accumulated) followed by a minimum 45min break and then another 4.5hours driving.
Twice per week this can be extended to ten hours driving so long as the driver takes a second break of 45min before his second 4.5hour driving period has elapsed.