Thanks for replying Scott, so I think that answer confirms there is really no such thing as a vinyl dye - only paint? (using a conventional definition that the the difference is that paint goes on top, dye penetrates through). To be honest I'm surprised those manufacturers make such a categoric statement given that its not really correct....but that is the reason I posted!

As mentioned, I do have a black top I could use, but not a curtain so either way I have to dye/paint the curtain - you actually don't see much of that.

I think I'll get some VHT (which is available over here), test it on some spare bits of vinyl from my top (I KNEW saving those offcuts was a good idea ) and see what it looks like.
If it looks GREAT - I'll spray the top as well and replace as necessary in the future.
If it is only passable, I guess I will install the spare top (more time.....will I ever get this car on the road ).

Sounds like the flaking/peeling I was worried about under heat/pressure from the top is probably not an instant issue, so that is a major plus.

Either way a new curtain can't be in the plan right now...so it will be what it will be..