They became intermitent at first, now they're either on or off, stopping halfway on occassion. The automatic setting does not work anymore. I've checked and cleaned all earthing points, apart the 1 in the boot (can not find that 1) thats sorted all the other electrical problems, yet the wipers do not reset themselves back to their ''rest'' position.

You have a problem with the wiper motor or the wiper switch.
If the switch is faulty u can usually tell because u can get the wipers to either work or stop by very gently touching the stalk (poor contacting of the switch) without actually moving it a position.
Otherwise l would strongly suspect the motor.

If u remove the wiper motor u will see that it is a motor on a worm drive,.
At the end of the motor where the electrical connector attaches is a flattened circle, this houses the worm drive & pinion that the wiper linkage attaches to. Inside is also a set of circular tracks, there r breaks in the track that act as the stop position for the wipers (the breaks cut power to the motor to stop it).

These circular tracks could be dirty or scorched from arcing of the contacts thus causing problems with the operation of the motor, there r 3 tracks for each of the speeds (fast speed is a full track, normal is a track with a resistor in series to slow the motor, & intermittent has a resistor in series & gaps in the track.) so damage to these tracks can affect all speeds in odd ways.
Since u have already checked the earth points u r obviously not shy of tackling the problem yourself, so remove the scuttle panel, then remove the wiper linkage & motor.
Seperate the linkage & motor & remove the cover from the motor tracks. If u cannot see any obvious dirt or damage to the tracks then u will have to replace the motor.

Thankfully as this is a '98 model 306 it does not have the more complicated multiplexed electrical architecture, & so u avoid the possibility of BS l or Comm2000 problems.