OK, so I have carefully removed the various patches over rust, most of which are close to the door pillar. The bottom of the door pillar has had quite a few little rubbish patches welded all over the place. However I found you can get a great little repair panel for this as shown below and it is not super expensive.
To replace the bottom of the door pillar outer, it seemed easier to remove the wing to door pillar closure panel by carefully drilling out the spot welds. This panel has some rot on the bottom, so I will need to fabricate a repair section for this as well.
Here is the finished area with all of the patches removed. From here I have trimmed out all of the rust areas and trimmed the bottom of the pillar on the outside to fit the repair panel in.
A lot of head scratching to decide the best way to get a good tight fit and keep as much original as possible. Not a job to rush here as the joints need to be as tight as possible.
However, not going to weld this on yet as there is a repair to complete on the inner skin.
Here I am making a repair panel in one length for the corner here. I have used a joddler to get a flush finish n the outside, and this will put the repair overlap on the inside.
I have not cut the outside of the panel to size yet as I need to make a repair panel(s) for the inner wheel arch to meet this panel.
The panel in place including the door pillar bottom clamped.
I am not a metal fabricator, but I am very happy with how this is working out. All of the work on this has only really taken about 6hrs so far.