[grumpy]

Ant,
It's the same in the world of composites as elsewhere, why mix unlike components. If you do you will possibly suffer the consequences.
The finest material going in every day auto body composite materials, is simple polyester gelcoat surfacing and isothalic polyester resin with woven roving.
Why use vinylester, while it's cheaper than iso, it has different properties and so does the epoxies. While all of these resins will stick to anything, they will not bond to each other necessarily.
grumpy