Recently found your channel and it seems I have had the same problems with my C5 as you have with yours! DLR's & hinges... I did my front and rear hinges last week for the same reason. Got them from eBay China and they had OEM Citroen labels hidden under a paper cover label. Result! I found the rear hinges very easy to do. I used two heavy screwdrivers to fold the mechanism into the closed position before fitting the rear which can then be fitted with the door shut. I supported the front door with a jack to fit that one because it can only be done open, but had to faff about getting it aligned so that the door would line up correctly.
I accidentally dropped this conical part inside the door when replacing the front hinge ( I don't know the purpose of this part) . Now it makes annoying clunk when closing the door :) I also bought on ebay from Lithuania, not satisfied with the quality
I have no idea what the conical bit is for either. It sucks when something falls in the door. I had clips fall into the bootlid in my previous C5, and it was rattle rattle rattle every time I opened it. I've bought a lot of stuff from Lithuania for my C5s, and I've been generally happy. I hope I continue to be so!