Saw this thread pop up and realised I never updated on the reply from DecalGirl.
Basically, they will let you design your wrap in any colours you like, but they can’t print neons (and, it seems, a lot of other colours) so the printer just produces the closest it can. They do have pre-printed sheets of neon vinyl which they use for single-colour wraps, but you can’t have them customised at all.
Anyway, they were very apologetic and offered me a refund or said they could send me a new wrap with the pink as ‘bright’ as they could make it. I went for the latter.
I’ll be honest, it’s still purple rather than pink. But it’s grown on me quite a lot… and it does stand out more against the sky than the grey body did.