How do I bathroom / kitchen / extension? etc.

If you're after a non-ogee profile, probably one of these sorts of things. I'd say you would want something taller than 45mm, it'd look kinda odd. For ref, skirting is usually 120 or 144mm high.

Unless your plastering/tiling is already down to the floor, then you could leave it without and see how you go without any sort of baseboard at all, but you might find it gets kicked and cleaning around it would be a pain without marking the wall.

builders depot will have a big range.

Also look at architrave / door trim. Our original skirting was architrave / door trim which I liked because it's slim. So that's what we had fitted when the floor was done, much to the confusion of the fitters.

Still needs another coat. #snagginglist

I’ll try and take some pics of mine because I’ve just redone my bathroom.