I actually have a nice set of aftermarket decals - so it's not a problem for this build in that regards.
I was just really seeing if this lamp I bought was up to the task of bleaching the decals, like some people use those nail-dryer things for, but alas it seems not (so far). I will, as you said, bung them in the window for a bit just to see how long it takes - although I've not had much success with this method either - hence the idea of the lamp. In reality, I was just experimenting (as you do) to see what I could do with old decals if I come across them in the future. Normally I just buy replacements.
Airfix of old used to make some nice, if basic. modern jet kits - it's a shame they don't get a bit more love. I hadn't heard they'd lost the tooling though - that is sad. This one looks like it'll be a nice, if a bit inaccurate, build.