The answer was a combination of all your suggestions. Reduced Layer Height to 0.2mm, reduced Other Layer Temps to 250 (down from 270), preheated the chamber to 40C +, double checked Brim settings, AUX fan off, Chamber fan stuck at 10%.
Thank you everyone for your help:) @b3rnie @JonRaymond @StreetSports @EnoTheThracian @KanneKaffe