Again, thanks fellas, for the encouraging words.
Re the spraying, I popped the model on the turntable in the booth and wafted mist coats of W&N (20% water mix) over the wings. As it dried I wafted some more and at that point I saw the bumps rising in both roundels and immediately stopped, lifting the turntable out of the booth and looking closely to see what was happening. Then I pierced the bubbled areas with scalpel point but without desired result of decal snuggling back down. Since hair dryer had worked previously I very gently tried this and decal did flatten but with bulges, cracks and veins appearing. W&N Galeria is about the most chemically neutral varnish I use and there was no MicroSol/Set/etc anywhere near these markings.
I'd just say, I've been modelling for over 50 years and won a few medals here and there but never had decals behave like this before. I've wrestled the old Blue Rider thick decals into submission, I've succeeded with some of the notorious Roden lozenges - but this sheet from Special Hobby was the worst in my experience - yet they looked so good before application.
I've got an idea how to proceed, but a wee break first methinks!
Cheers
Sandy