Thanks Gaspen for the advice. Unfortunately, I have already cut the steps on both sides. The reasoning behind that was to install the new steps and use them to reference the new sills. I have taken dimensions of everything, so it should be fine (I hope). In any case, that is good advice and if I have seen it before I would have done it like you said.
Progress after today's work. I completed the bracing of the cross member to ensure it stays in place while I'm replacing the floors and sills. Looking good I think...


Next, I started cutting the steps (sorry Gaspen), leaving enough material in the corners. I have the driver's side step and A-post repair panel, but I still need to order this side (Iinitially thought of retaining it, but there was a lot of filler I didn't see before). I decided then to replace this side as well.


That gave me the opportunity to look inside the cross member and as expected it is in very good condition, with no rust inside (Yay!!!).
Next, I started to cut the floors off, leaving enough material near the central tunnel to reference the new floors. Once I receive the repair panels, I will cut it to suit.


That left a big amount of rust on my garage floor...

And finally the front floor, following the same procedure.


As a result, I have a few rusty panels that I need to take to the recycling centre...

I also made a start on the driver's side, but I didn't take any photos. More updates next week!
Cheers.
Victor.