Several leak points, but to get you started, rear window clips, if you feel inside the boot beneath the parcel shelf, you'll feel plastic clips. These can leak. If you lift the rubber trim around the rear window, you'll see them.
Also the side trim along the wing can leak. Hinges have also been known to leak too. Good job MGR never made subs
If you use the Google search function at the top of the page & type boot leaks, there's reams on the subject
Have fun
