Yeah the cracks id chases out a little with a Stanley so the filler had something to adhere to. The one by the window I think was movement, the one by the corner of the door a lot of plaster fell out / it hadn't bonded well.
I was impressed with how tidy I got around the window below!
I rate that filler for small cracks etc. Otherwise use polyfill etc as a "first coat" to fill a wallplug hole etc.
Bedec Aqua Advanced Satin Paint - can get from toolstation.
For what it's worth, id recommend a water based gloss like this one as it means it won't yellow in a couple years like oil ones. This satin gloss is easy to apply and finishes well. See my pics above or this below (all the skirting, the window, the architrave done with this)