Accepting your point concerning heat this is common. Several people have added additional bonnet louvres to reduce heat when standing. Several have also added them because they are pretty. Whoops did I say that out loud. I have never seen evidence of the impact when moving but after you have parked you can feel it through the vents.

The S2 and Coupe do both get a load of heat soak and high under bonnet temperatures at rest. As the car heats up the gearstick can become pretty hot to handle as I had a metal ball knob fitted, I disliked the factory one. Additionally the footwell surrounds and the chassis frame below the door can get pretty warm as well. Great in winter!

If it is really hot I tend to pop the bonnet knobs at the windscreen end which lets the heat out faster and does not really show. Never had anyone look or touch as they get nothing but love.

On the Coupe the breather valve for the tank goes to a pipe which exits down past the tank to the road. On mine it was kinked at one point and so the pressure could not release. Just as a check did you test that one? The cut off triggers constantly when filling following my last service and adjustment at Williams. Uttlerly pisses me off, not to mention I can no longer go more than 90 miles before risk of running out of petrol. It seems to be a magic combo of breather, angle of the neck mounting on body.