Thanks for looking in Ken.
Determination has finally taken over and this HORRIBLE monstrosity is going to be finished.
The floor pan and body are both terribly warped.
Each one only has a 4-5mm 'twist' but it meant that when the two parts came together there was a gargantuan 8-10mm gap in the body to floor join on the drivers side.
The only 'fix' was to create a couple of plastic blocks on the floor pan at the outer edges, just behind the front wheel arches.
The body sills were then drilled through and into the blocks being held in the correct place, and small screws were put in to hold it all together, in shape.
Miraculously, it worked. You can see the little screw heads in the pics. Not much I can do about that and TBH - I couldn't care less.
Some little bits of trim and stuff to add but then it's DONE...!
roymattblack attached the following image(s):