Ask around for a good and trusty welder who knows about his job.
I've seen some very nasty & lumpy repairs of this common BX problem.
The last repair job I got done on my TRD is looking perfect - and the hinge is solid - no movement on the pillar while door is moved. My welder is not a Citroen specialist - simply a good craftsman.
You may help the welder by preparing the job this way :
1) unclip the headlamp on affected side
2) unbolt the blinkers lamp same side
3) refit blinker using gaffer tape - clip the headlamp back in
4) now you have access to most of the bolts/nuts holding the wing - remove all bolts/nuts. Clean & greas the bolts nuts - then refit 2 of them handtight to keep the wing located
5) pay special attention to the 2 bolts at rear of wing accessible when door is partly open. These fits into captive nuts.
6) support the door then remove door hingepins and insert screws or nails which are easy to remove at will.
7) support the bracket holding the pin for the door strap. Then tap out the pin. Insert a nail.
8 ) strip the door and unhook all electric connectors - then withdraw complete door loom with the gaiter from the door.
Now the door and wing can easily be removed using no tool.
Only a very brief explanation is needed to get back a perfect job.
This ensures that you dont get your car back with all sorts of minor damages and shortcuts which have to be repaired - like a bunch of cutted wires to the door
The main idea is of course that you try stay in control of what happens to your car !
C U / Anders - '90red16riBreak - '91GrisDolment16meteor - Project'88red19trsBreak
dead cars : '89white 16RS - '89antrasitTRDturboEst - '90white19triBreak