Can I remove standard plastic casing ceiling light rose and replace with metal version with hook?

The metal hook plates must be earthed! Similarly it is strongly advised that they are not just simply screwed up to cover the existing ceiling rose. The whole ceiling rose should be taken down and the cables carefully connected into Wago or Hellerman maintenance free spring loaded connectors before the hook plate is installed. Remember as you'll be doing DIY alterations to the wiring, you need to register your intent with your local building control department and pay their fee (typically around £200-£300). Once you have consent in place you can do the work and on completion an inspector will call round to check and test its ok and issue a part P certificate.