My pours are looking much better in the last week. I identified an issue in my distribution. On my final sweep/level I was pushing extra coffee to the far side of the portafilter, Im just being a bit more conscious about pushing it into all the edges and my pours are looking better. Im also tamping a bit more carefully and incorporated a polish which seems to be helping.
I have also made pre-infusion a habit. I hit the brew button now with the steam valve open and close it when water comes through the arm. It only takes a couple of second but I think it achieves the objective of allowing any headspace in the portafilter back up through the group to fill with water before being hit with pressure.
Apologies Silvia I shouldnt have doubted you.