All the underfloor stuff is now removed and I've started to clear away the old underseal and rubberised sealant, which is a really messy and time consuming job, two days into the process so far..
Thankfully the floor is in really good shape, a couple of areas where the sealant was starting to let go but a bit of treatment is all that's needed. Only area so far that I've uncovered to need welding is where the fuel filler tube sits there was a piece of protective rubber sleeve on the chassis seam which had trapped moisture, shouldn't be a bad job to weld up.
Hoping to get the rest of the floor cleared tomorrow then I'll weld that area and clean the rest. It will be etch primed then seam sealed before stoneguard renewed all over. I've decided to paint the underside in body colour rather than it be done black, or in underseal.