I’ve finally got that rise!

I have been baking sourdough for about 6 months and had been enjoying my loaves but they were always a bit flat a bit dense – but still delicious.
I have finally got that open crumb and rise that I was hoping for! Some of the things I changed which I think made a difference:

—changed flour to shipton mill Canadian strong white flour (I was using Doves farm strong white before and I do think the flour change might have made a big difference?)
—use a scalpel to score the top (I think I was scoring too deep before with a knife)
—increased my bulk fermentation time (I’m in the UK and my kitchen can be on the colder side so seemed I needed a longer than I was fermenting for before).

Not sure which of these changes or all caused the improvement – curious others’ thoughts!

Recipe:
Flour: 540g
Water: 360g
Starter: 120g (fed 1:3:3)
Salt: 12g

Mix everything together and kneed briefly, rest 30 mins then four sets of four stretch and folds over the course of 2-3hrs. Leave bulk fermenting for a further 7 hours (roughly) then shape in a banneton in the fridge overnight. Bake 30mins Dutch oven lid on, 20mins-ish oven lid off.