Right I've been back to the company I got the paint from and got an unusual tale......
Aparantly the boot lid was scanned at one branch and the formula for the paint derived from the scan, this was given to the other branch to mix the paint. The problem is the formula was for 2 pack, not Cellulose. The other branch in their infinate wisdom made the paint up in Celly as I asked but using the formula for 2 pack, which ends up the wrong shade.
I've been told that the only way they can get a match is to use 2 pack, but make it up as if it was going into an aerosol which in effect makes it a 1 pack paint, thinnable with cellelose thinners. I'm assured it won't react with existing Celly and it is as safe (or dangerous whicih ever way you look at it) as Cellelose. It will be a couple for weeks now untill I can collect it as it's a bit of a trip, so I won't know how good it is.