UV Restore of Yellowed Decals

Ken, @Levent Suberk's video posted, although excellent advice has a caveat listed in the very beginning,

Video wrote:Warning!
This tutorial is excellent only if:
Your decals are not yellowed and uncracked

Which, I think is the reason why you further posed the question.

Yes, I am familiar with your experiences, letting kits get old before building. IMO, about the only way is to scan the decals, clean up or create a non-yellowed non-cracked image file, then have them printed or go to someone who already has high quality duplicates available.

What kit are you building now, that needs decals rescued?

In the past, I have been able to find Hobby King had decals for their various scale ARF's available separately. By my selecting one that was sized close enough could rescue a scale job. But, times change and stock availability keeps shifting. Plus, shipping from Hong Kong when unvailable at US store location is now too high to make it worth it.

To fix cracked decals try that method in video.  

Acrylic clear spray also works. I don't use dope on decals because dope dissolve decals. Even and heavy coats are necessary, a mist of clear coat isn't enough.

Ooops I forgot gallopingghostler's question. I have been building Airfix Sea Hawk issued in 1971.