I finished the battery tray this evening and I am really pleased with the results.
My biggest worry was that I was going to have to replace the whole section which was way more complicated than what I had planned. Fortunately it did go to plan.
First job was to check to see where the bad metal stopped. On closer inspection I realised I did need to cut more from the back wall.
I just wasn't happy with the pitting. That needed me to drill out some more spot welds the from other side and then cut back to good metal.
Next job to clean up all the waxoil as best as I could, which took a while using a brush and lots of Gunk degreasing agent. But it did evenually come off with a load of elbow grease as well.
The flanges that the tray sits on needed to be made good before I could weld the tray on.
Next was to make the template and offer it up.
Then to start to weld it in.
And finish with primer.
Really happy with the results. Also managed to fix that hole above the tray. I think next stop will be the footwell toe panel.