From what I can see, it appears that you have two layers of primer. One a dark gray and the other a lighter shade. I say this because it looks like they scrape off readily, like paint tends to do. Gel coat is normally about .020 in. (.5mm) thick and is as hard and brittle as polyester resin, because that's what it is. It's also not readily separable from the remainder of the laminate. It shouldn't scrape off cleanly leaving the rest of the laminate. That's because the entire thing is built up in short order and the gel coat is chemically bonded with the rest of the laminate as it cures. Of course that doesn't mean that you can't scrape through it with a nice, sharp Sandvik scraper. One of my favorite tools.
I've used gel coat quite a few times in boat repair. It's basically polyester resin similar to that used in the structural laminate, but it's optimized for color and exposure to air and UV. It's the colored surface you see on production boats. It maintains a pretty good gloss for quite a while, and when it finally oxides, it can be sanded with fine sandpapers and then polished back to a nice finish. But it never looks as good as a good paint job in my mind. I think clear gel coat exists, but I've never seen it. It's virtually always used as a color coat.
I think our cars are made like this: Plain, un-tinted polyester resin is catalyzed and sprayed into the mold. [If it were not to be painted, this would be gel coat.] After an hour or so when it has begun to cure, resin and fibers are dispensed together through a "chopper gun" which chops the glass fibers and mixes them with the resin and catalyst and sprays the mixture into the mold as a second layer. And that's it! The first layer with no fibers is just to establish a smooth surface with no exposed fibers when it's de-molded. It gives a good surface (at least theoretically) for priming and painting. So I don't think that there's any gel coat. I don't think there's any need for gel coat. But it doesn't really matter.
My point is that you don't need to go out and buy 'gel coat' to make some repairs, or concern yourself about what part is gel coat and what isn't. All the stuff under the paint is polyester, and 'regular' polyester resin will suffice to make the surface of your laminate. I suggest that over that you should use a high-build sandable polyester or epoxy primer which can be sanded to a fair finish as an interface between the laminate and the paint.
By the way, as JB intimates when he says "high" quality, it's really not. This is about the cheapest kind of fiberglass structure one could make. The reason for all the stress cracks is that the ratio of resin to structural reinforcement (glass) is very high. There's way too much resin in these laminates. High quality laminates these days (becoming quite common) are made in autoclaves and with vacuum bags to extract as much excess resin as possible before the laminate cures, leaving a laminate that is light and high-strength.
I've recently used a resin I like quite a bit. Maybe not available in Europe. It's relatively thin, so wets-out reinforcements well, and cures water-clear (not sure that matters). It's marketed as 'surfboard resin': Silmar 249. A resin like this needs a mold release (PVA) sprayed over it to inhibit air for a full cure on the surface after application.
I suggest: grind the area with cracks that are large and seem to extend through the laminate, deep enough to put a layer or two of glass. If you think you need 2 layers, consider making the first with cloth as it's stronger than mat, but by itself would 'print through' to the final surface showing evidence of the weave. Reinforce with cloth on the back-side if accessible. Try to keep excess resin to a minimum while still wetting-out your fibers fully (a plastic squeegee can help), and then use the very lightweight 'veil' (~0,75 oz.) over the more minor stress cracks. I'd use a foam roller to thinly apply resin, then the the thin cloth, then go over it again with the roller to make sure it's fully wet-out and smooth. If you're using a better-quality resin than the one from a consumer auto or marine store ("non-air-inhibited") you'll need to spray PVA mold-release over it so it fully cures. If you're using resin with wax in it (auto-store stuff), that will need to be carefully cleaned with acetone before you sand it or put anything else over it. PVA washes off with water. If you're going to do two layers, you don't need the PVA until after the final layer.
Any bonding of new resins is mechanical, so things should first be very clean (acetone) and then well abraded with coarse abrasives before applying resin.
To summarize: Like JB said.
What else can I say? I've already said too much!
