Roof panel with rust spots

Well bit more progress on my Alpine White Campaign

I have had chance to examine the roof panel more closely j now the car is back on all 4's.

It's riddled (perhaps bit overstatement) but these rust spots are actually penetrating the panel - not just a good tee-cut try to remove.

Plus the sun roof aperture is, well rotten too.

Has anyone tackled these jobs successfully? It looks problematic to repair the roof panel & sunroof/drain channels.

Ridiculous thought - but is there any chance that there might "one" out there that are new/old stock? 

Is a replacement "chop" the answer 😬 ? Assuming there's a shell out there that has a good one that can be cut off. 

Any help / pointers gratefully received.

I've fitted the complete "cassette" into a Mk1, which was cut from a mk2 golf. It's not really a diy kind of job, but do-able.