I am about to don this very job. My Xtype doesn't have the wood effect trim. I found two pieces of trim for both front doors at a scrapyard for £8 (pair). When I took them off the scrap car I noticed that the leather in the inside of the door where the trim fits has been removed (to allow the trim to fit into the leather rather than sit on top). The door panel also had the three slits ready cut and has three holes in the back of the panel. My car doesn't have the slits but it does have the three holes in the back of the panel so I'm taking the following approach.
I made a cardboard template so that I had the shape and slots for the fins on the back of the trim. I will then position the template and cut through the leather with a sharp scalpel and then, using a small drill, make holes along the length of each slit. These will line up with the holes in the panel. I will then attach the trim and use the retaining clips on the inner side of the panel to 'pull' the trim into the leather.
I hope this helps I will take pictures of the process.