Hi Ronan,
I have made a simple spark erosion apparatus based on the original idea of Deryk Lynas. This uses an oscillating spindle.
**LINK**
My version is a low power version based on a 24V laptop power supply and it will erode a 3 mm diameter hole at the rate of circa 6 mm/hour. With a higher voltage power supply (Deryk Lynas used a 50 volt transformer giving 70 V dc)the erosion rate would be much faster. The advantage of the Deryk Lynas method is that it is mechanically simple and it has simple electronics.
I have upgraded the original version with a mechanism to maintain a constant maximum spark gap, see
http://mikesworkshop.weebly.com/a-spark-erosion-apparatus-mk-3.html
Mike