To remove the rear corroded panel cleanly and to fit a rust free front brace, In my shop I would charge a total of £150.00 inclusive.
Best to get a garage to remove the panel who is not carrying out the MOT test.
You will not have to go through this every year.
Simply replace the front x/member with a rust free second hand one (which I have in stock) and dispose of the rear panel.
Job done, simple.