I'm not so happy about the epoxy compatible gelcoat GV50
When mixing with 5 to 10% the gelcoat looks matt, even so it is too thick to be sprayed in a standard 2.5mm gravity fed spray gun and then it is polyester mix, something I really distaste.
additionally, I can't overcoat it  no matter what waiting time, running into danger that it either blisteres or does not adhere to the first coat.

Don’t laugh but I’m a fan of How-Do-they-do-it, watching it all the time just to see what is around and getting ideas what to try in my field
I'vebeen watching people using gravity spray guns coating the mould in paint/gelcoat, most likely 2k and then adding the fabric for either pre-prep curing or infusion without any problems.

Has anyone any idea what they use. As far as I’m aware, Epoxy has very good adhesion to near anything at superb strength except “poly’s”

Thanks in advanced, that will be used in none permanent water submersed marine equipment

"when mixing with 5 to 10% "   polyester pigments - sorry

It depends on the chemistry. Epoxy won't bond well to a lot of things if the surface prep isn't there, unless they are chemically compatible and form a chemical bond with each other. Trouble is, there are so so so many different chemicals in our industry, that unless something has been specifically formulated to work in the intended way then you are experimenting. I've tried using several different automotive (so polyurethane) 2k clear coats as an in-mould coating, but didn't have any success with them. The coatings delaminated from the finished laminate very easily, they never even survived trimming. 

I've gone away from in-mould coatings. I used to use Duratec Sunshield and Scott Bader Glosscoat (both polyesters) all the time, but they are utterly rubbish for UV protection. So then I used to post-finish them with a polyurethane for the UV protection - essentially I was doing the maximum amount of work and adding as much weight as I possibly could. These days I prefer to just post-finish with the polyurethanes. Less material/weight, less work, better end product.

thanks for your feedback, Hanaldo
You confirm what I was thinking to do too