Well thanks to a host of people, I now understand the answer to your question (since I asked it after a disaster of a print a week ago). The strange thing about printing is since it is so finicky the automatic adjustments aren't made in software like they are in say a laser printer or ink jet printer for print density. What you need to do as you raise/lower the layer height is compensate with more/less filament extrusion. The easiest is to simply change the extruder multiplier (I set mine for 0.9 with a layer height of 0.15 for instance) and turn off extra restart distance... Those made a world of difference.
Thanks I imagined it would be a flow issue. I will have to give it a go tomorrow/Monday. I have my extra restart distance off anyway so that's ok!
