YYIPPPPEEEE finally sorted this out.

Worked on it from 8:30 till 3:30  - ended up being the relay on the PPB board was stuck on one side - from what i understand this meant it wasn't switching from left to right but rather switching left AND right at the same time (ie: firing two switches - the outhole coil every time another switch on the bottom half of the playfield was triggered in this case).  Ended up scabbing a relay off another game and it worked fine

For interests sake and reference i found a few other interesting things....one of the small relay assemblies was testing strange on one of the legs - it turned out that once i replaced the IC  that was further 'downstream', the resistor assembly all tested OK - i assume this was because there was an internal short in the IC causing the strange readings.

Anyway, learned a heap more about these beasts today and was a great feeling once i got it sorted.