Got a good chunk of the underneath done, so here goes:
Finally got some paint on the arches! Two coats of POR-15 and it's come out really well:

I also blow torched and scraped off as much of the underseal and seam sealer as i could, then sanded a section of the floor, primered it, then gave it a single coat of Frost's Chassis Black:

During this i realised how poorly the sills had been fitted. With only small sections of welding, with the rest of the gaps joined with some kind of flexible filler.

So Kenny came round today and got a lot of welding completed. This is how the sill should have been finished. We also removed the jacking points which are completely pointless and replaced them with plates:

This also covered the hole in the driver's footwell:

The welding on the underside of the boot floor is now all done:


and the new subframe mounting plate is in place

Next step is to finish removing the muck from the underside, then seal all the seams. Paint along the seam area (where the rust is) with POR-15. Rub down and prime the underside in sections so i don't have metal exposed unnecessarily, and coat the primered metal in chassis black. Once it's all had one coat of black, i'll give the whole lot a second coat in one go, maybe even a third, then the underside is complete! It should be completed in two weeks providing the weather holds goods for me.
PS. HOW cold is it out there!