Dougefresh, the only issue with that will be your power usage...not the most efficient...AND since the temperatures that heat lamps provide change as the room temperature does...its not the most accurate way either.
Gomez is correct though, flexwatt does function much more effectively in rooms that are heated.
What I like about the heat tape over the heat cable is that the heat tape evenly distributes the heat over its whole surface, whereas heat cable gets very hot in a small space and doesn't radiate that heat as well as the heat tape does. Many have used both successfully and it all depends on the specific application of it.