So tried the new setting suggested by support:
''If you change the printing temperature for PLA to 205 and increase the extrusion multiplier to 1.1, combined with the starting G-Code I gave you, it should come out much nicer for you''.
Ran my usual 20mm test cube - came out fine.
Then ran a large model from my collection: http://www.thingiverse.com/thing:550314
with same settings as the test cube but after 10mm or so of printing, i experienced under extrusion/clogging nozzle as i've found so far with S3D??
I just know its my error but for the life of me i can't think what else to tweak?? I've sent another ticket to the very helpful Hai Pham in support - awaiting to hear back
Keep you posted