so i removed all the mylar with no problems at all. No insert decal damage at all.
I used a product called "goo gone" I imported some from the U.S.A. and it was well worth it.

How hard was it to get the "Goo gone" - I 've seen it mentioned elsewhere with glowing reports but never found it is Aus.
I have a recalcitrant piece of mylar that I can't budge.

Can you share the details of how you got it?

There is another product called Goof Off which you can get at Bunnings etc but it is much harder and dissolves things.