Can I decorate this skirting board install?
As for the gaps between the bottom of the base board (skirting) and the floor ... that is normally covered over with a base shoe molding. Base shoe is a small dimension molding that can be pressed down to fit the variations in the floor surface. Base shoe molding is normally only skipped when carpeting is going to be installed on the floor.

A nice trick regarding base shoe molding is to fully paint it (primer plus top coats) before it is installed. This way, after install, all that needs to be done is to fill the nail holes and do very small touch-up painting. It makes for a really clean look along the floor. If a pneumatic nailer is used to install the base show the nail hole size is minimized.

In days gone by it was common to just use flat boards for skirting instead of the types in common use today that have the top shaping features formed into the skirting. This allowed for the use of an additional small shaped molding called the top cap to finish off the top edge. Similar to the base shoe, the top cap was flexible and would cover the gap between the skirting board and the wall. In those days the idea to squirt calking compound along the top edge of base boards was unheard of.