Only that it must be well watered before you start to empty it out of the bag. the stuff is terribly dusty and unpleasant in its dry state.

Good advice, thanks! Do you think it will conduct the heat as well as sand?

As water is a good conductor of heat it should do the job equally well. Perhaps you might consider putting some kind of reinforcement under your propagator because, even though Perlite is a lot lighter than sand, it will still be heavy from the weight of water.

Did not have time to type much before. but agree with Balcony, even perlite and water is going to be heavy, with pots or trays of cuttings etc on top of it. My propagating frame is based on 3 feet by 2 feet paving slabs on 3 inch fence posts.

I doubt any 'normal' greenhouse bench will take the weight of either sand or perlite when wet. Follow Owdb's advice and create a good solid sturdy structure.

Thanks for all the good advice. I will certainly add more support under the bench. However, I am still concerned about the conductivity of perlite. Presumably damp sand is recommended because it works well with water whereas my concern is that perlite is a good insulator and may prevent the warmth from the cable?
I contacted Parasene and they didn't even bother to reply!