A new element comes with the two thermostats. The elemet is wired through one thermostat to one side of the element and direct at the other side. the direct side is easy to spot as there is a short spur that goes to the non-in line thermostat.
The problem is that the connectors are not rated correctly in my view, if you find this then upgrading the connection may help.
Follow this at your own risk etc etc
Mark, September 2005