I think I've answered it:
Make a calculation in a cleaning step along the lines of:
if [location]="start" then [latitude] end
same for longitude.. and two more for the end locations
Then group the location types together.
I would start a little different. Before joining the tables, I would take the location table and split it into two tables (Split, then filter out one condition, change column names). One table would have only start locations and one would have only end locations. I would then join those two location tables. Then I would join that new combined location table with the driving jobs table.
I think you're right - my method only groups the start and stop, it doesn't combine the rows.