I have the same problem with my Orion Mk1 S2 RST. If I get stuck in traffic the temp goes up exactly below the red mark. The only difference is that the engine doesn't cut out, but if I switch it off at that moment I get the radiator water coming out. I think the problem is because the exhaust manifold and the turbo are too close to the radiator.

Next week I'm going to install a different fan switch and a turbo heat shield. I will also be checking the radiator and if it results in any minor problem I will put it the Pace Alloy Rad. Try doing these things mate. You can also change the expansion tank to a S2 one.