Ok, I got the valves checked. They are fine.

In fact the heat in the legroom is not comming from Hit Air, it is actually the area below the steering wheel which feels very hot/is emitting heat, not blowing warm air as it would be from a heater.

Is this normal? It happens when I drive at faster speeds and also when I go uphill in the V8. Could it be a cooling problem?

Try to see how warm is the area under your steering wheel all the way to the pedal almost. it is a bit warm as in lukewarm when I drive normally, definately emitting some warmth, and when I push the car the area gets quite warm and I would say it feels like a fever.