I took my F-Pace in for service on Monday and am now missing my J off Jaguar!! What should I do ??

 

You buy a new “Jaguar” appliqué. Remove the existing “Jaguar” and replace it with the new one.

Or de badge the car.

 

The dealer does not sell the individual letters ... you have to buy the entire set.
You may be able to find a "close enough" J on amazon or hobby websites, or if you have a friend with a 3-D printer and an air brush.
If you are going to remove the badging dental floss will do it rather easily and you can use makeup remover wipes to pull the remaining adhesive off with a little pressure.