Finally, I got rid of so hated number plate frame that the dealer fitted before my car collection. Due to the holes bored in the number plate in the "wrong" places, I was unable to fit it directly on the hatch, so I had to pay £76 for a new number plate. So much for a cleaner look.
Then I replaced spigot rings on the front wheels with the new ones with a narrower bevel. Now the wheels have better support and vibration that I mentioned a week ago seems to be gone, though I'm still testing.
At last, I replaced the grey star looking wheel centre caps with the round black ones. I don't know if I like it or not, buy I damaged one star centre cap when I took it off, so I didn't have a choice anyway. I can fix it though.