Update:
After having had a chance to try the car over some favourite roads it's a good improvement and definitely much smoother.
It still needs to be kept above 2,700 rpm but is a quicker and easier drive.
When "making progress" it feels livelier and I sort of feel I'm pulling back on the throttle rather than pressing on to maintain a decent speed.
The rev limiter is softer, mre of a gentle nudge to change up rather than a smack in the face.
One unexpected side effect is it set off my neighbours car alarm as I backed out of the drive - that'll go down well for any early starts
Overall not as big a step as stock to stage 1 but a worthwhile improvement.
And a huge

to Dan at Krazy Horse for the fitting and dyno tune. He really knows his stuff and is a font of knowledge on all things M3W (and ecu).