What are the symbols in the picture?
If the symbols have any defined meaning in the auto electrics business I do not know but we can make a few guesses at what they are likely to signal.


Window wiper symbol at the bottom is obvious.
Motor on the right is obvious too. This has three terminals so it represents a two-speed motor and so the controller must be two speed.
Transistor symbol indicates that it is electronic rather than, for example, a bi-metalic strip type for the intermittent function.
Pulse suggests that it has an intermittent wiper function.
Switch with what appears to be a cam actuator probably represents the self-park switch input. When the motor is switched off in motion the cam maintains the park contact until the wiper is in the park position. The contact then opens and stops the motor.



  Do you know what components a screen wiper control is composed of please? 




Figure 1. A Chrysler intermittent (delay) windshield wiper module undergoing surgery. Source: Siber-Sonic.

A relay to do the heavy switching, some diodes, resistors, capacitors and a transistor. A modern unit would probably use a simple micro-controller.




  So if the speed is selected by the stalk I presume that is done by selecting a higher or lower voltage feed. If so then what controls the voltage? a resistor in line somewhere before the stalk?


No, if that were the case there would be only two wires to the motor.



Figure 2. A typical wiper motor circuit. Credit: Jim Mais.

Note that the high-speed connection goes to a third connection on the motor. The internal winding and brush arrangement makes this the high-speed option.