A couple of pictures would help, Mick. I think I know which Villiers 2 stroke you have but there were variations. Pictures also help other members understand your problem.
I suggest you begin by removing the flywheel cover and checking the points for gap and condition. They may have closed up due to lack of lubrication of the cam that operates them, they may have become burned or fouled, or they may have been badly installed to start with. I had one that came to me with what was probably the wrong moving arm, so it met the stationary point at an angle, and had no hope of decent conductivity. While you are sorting out the points, carefully check the wiring connections - they can come loose and/or corrode.
If it isn't the points or a bad connection I suggest you try a different condenser - they don't give much trouble but are probably the next best bet, in a case like this where it did run but stopped. However the remaining possibility is that the coil has failed, perhaps due to the wire's insulation breaking down causing a short in the secondary.
