OK back to the wipers
Below is the sierra rear wiper circuit diagram in the Haynes manual :
165 is the stalk, showing only those terminals that are used for the rear wiper and rear washer
161 (IMPORTANT) is the rear wiper intermittent relay
164 is the rear wiper
I've removed the ignition switch, ignition relay, etc to simplify. All power comes from fuse 15, which is energised with the ignition on.
With the ignition on and the rear wiper turned on to position 1 (intermittent), +12V from stalk terminal 54 is fed to stalk terminal 53A and then onto the intermittent relay. This in turn, using magic, sends an intermittent pulse to the rear wiper motor, which also has a constant +12V feed straight from the fuse to motor terminal 53A.
To get your wipers working intermittently, you will need to get a sierra rear wiper intermittent relay, not a front intermittent relay. This is because the self-parking works differently between the front and rear wiper motors.
Ignore what happens when the rear wiper switch is in position 2.
If constant +12V is fed to wiper motor terminal 53, the wiper operates continuously, as you determined yesterday in the quick lash-up you did with the battery and a few wires to the motor connector. Double check this, please, and confirm that this is correct.
So what you need to do now is change the circuit so that it operates when you move the motor to the front of your car, and works with the "Front Wiper" stalk controls. See diagram below :
The front wiper stalk (one down for intermittent, 2 up for twin speed wipers) now works the rear wiper motor on the front of your car. However,
1. the intermittent wipe speed is no longer adjustable
2. the rear wiper motor only operates continuously at a single speed - positions 1 & 2 of the stalk have been bridged, so the wipers will work with the stalk in either position, but only at the same speed.
I suggest after you've got a rear wiper intermittent relay that you again do a temporary lash-up to check it all works as I hope it should. You may need to add a couple of diodes and another relay, but we'll cross that bridge if we come to it.