Grant posted this before he was famous lol, and its what I use
Capellas Vanilla Custard 15%
Perfumer's Apprentice Dulche De Leche 2%
Ethyl Maltol, between 1 and 2 drops Per 10ml
It will look a light Straw Colour, give it a minimum of a week to steep, Cap Off, when ready it turns to a light orange
I mix my own juice but I've not been able to get my hands on any capella vanilla custard as it's always out of stock. The capella French vanilla (after steeping for at least a week) tastes very similar to GVC so I reckon that might be one of the ingredients.