I've got a pic of what's left of the C pillar for you Paul. I'll email it to you.
Well, it's taken a while but as of today there's no more rust! Woohoo.
I welded in the C pillar patch that I fitted yesterday.

And did the C pillar vents. I left the bottom one open on this side. No real reason why, I just did. The camera makes this shot look all rusty. It isn't. When you look at it in person it's all shiny.

Patched a small hole in the drivers sill.

Cut out the rust in the drivers footwell and bashed a replica out of a plain sheet of metal using a ball-peen hammer.

Then welded it in along with two other smaller patches.

I welded this one from both sides as it's lap jointed.

Then did some of the front seam welds.

Next job is the 30 or so internal plugs to replace the factory grommets in the floor pan and to plug up the internal holes in the C pillars followed by the chassis rail seam welding then i'll fit the rear tarmac arches.