Have injectors out, one self extracted due to broken hold down bolt. Extracted the bolt remarkably easily.

New copper heat shield/seal washers have a chamfered outer diameter that faces towards head, genuine parts with helpful diagram to show fitting position.

Not certain as to shape/size of seat. We have various seat cutters, a 17mm flat appears to just clean outer circumference of seat.
Don't want to get carried away until we are sure it should be a flat surface.

A good session on the google has yielded no positive results. Anyone know for sure, or how to find out?