Hi
The style of wheel you have is called proteus and you can purchase replacement centre caps from Just Jags although I'm sure the were about £20 each,and they are a different design being flat instead of slightly raised.
Also be aware the imitation split rim bolts are plastic which was an issue when I sent my wheels for refurb as they simply melted when dipped.
Some have found ways of replacing by buying small stud bolts and self tapping them in but I just left mine without as being kind of recessed you don't rally notice they're missing.
Hope this helps. enjoy your X Type they are lovely cars
Brian