Velux Windows replacement flashing adaptors

I wish to replace the old GGL 606 ( early 90's Vintage ) velux windows in our bedroom. They are fitted to the 45 degree pitch roof with Marley Ludlow interlocking Tiles. I want to fit Polyurethane coated SK06 units that are triple glazed for Rain noise reduction. Contemplating doing this myself seeing as it should be a straight replacement using the EKW twin combination flashing. I've googled the knackers out of all this and pretty sure these are the right replacements ( unless anybody reading this says otherwise. However the vendor I intend to purchase from online mentioned ELX 0000 flashing adaptors that would save having to re-do any kind of work to the inner window reveals. I've attached a picture of the window revels and old Liner. Could anybody explain what these Flashing adaptors do ( In Janet & John terms ) I downloaded the instructions from velux but not sure how these would save any work on the Window reveals ???
Also, are the BDX insulation liners a must or can this be done with Strips of earth wool or similar to insulate around the edges

Ok well the old skylights are set at rafter level. The latest generation velux skylights are designed to sit 28mm lower in the roofspace to help with the thermal performance. You can get a replacement flashing kit to keep the new skylights at the same height if you don't want to remove any of the internal lining.