Solved it. The domed bit at the top of the tap does unscrew, you need to be patient, clean any gunk off at unscrew by hand. but its not easy and you need to persivere...
I am trying to remove a cartridge from this basin mixer tap. Have removed it from the basin but cannot figure out how to remove the cartridge. I have a PDF from the Cifial website, but it doesn't explain how to do it, just shows diagram of the parts...any suggestions?