Thanks for the replies!
Sorry for not being more specific the first time.
The object moving along the path is an enemy AI sprite.
The path is the inside of a tubular tunnel (center is the vanishing point). So as the object moves towards an edge it gets bigger etc. So the thought process of travelling in a circular motion is so I can get the enemy to move from 1 side of the tunnel to the other without crossing the vanishing point (that looks weird). In total I have randomly placed 10 waypoints for each enemy wave and they should repeat until they are destroyed and so on.
The even positions in the diagram are easily calculated by going to the odd point and drawing a line to the vanishing point, where the circle and the line intersect gives you those coordinates.
I have placed a link to the capx below, but it's the full thing (warts and all). It also uses the SpriteFont plugin.
The scripts to look at are on the GAME sheet within the ENEMY_AI and WAYPOINTS groups.
Please let me know if there is anything in there that needs clarification.