DPDT Polarity Switch
simulate this circuit &ndash; Schematic created using CircuitLab
Figure 1. All you need.
How it works:

With RLY1 and RLY2 de-energised both ends of the actuator motors are connected to negative. They won't move.
With RLY1 and RLY2 energised both ends of the actuator motors are connected to positive. They won't move.
If only RLY1 is energised it supplies the positive connection and RLY2 supplies the negative. The motors will run forwards.
If only RLY2 is energised it supplies the positive connection and RLY1 supplies the negative. The motors will run backwards.