rusty floor pan

Hello my name is chris i own a bedford cf250 autosleeper diesel 1984 .I have just pulled it out of the hedge where it has been sitting for 2 years , and found rot on drivers side , very strange as passenger side is fine . Im looking forward to taking on the project of rusty wheel arches and floor pan with my clarke mig 90 .I am after a new inner wheel arch if it is available , i have been searching the net for 2 weeks cant seem to find one so looks like i will have to try make one ,has anyone tried to to make one on here , obviously needs to be seam welding on the bottom and can be plug welded on top any advice on how to do this would be great.
Many thanks chris

Rusty floor pan.