Setting up a propagation bench in the GH

OK, so after reading Specs thread on heating cables I've suddenly realised I can't do without a heat bed to take dahlia cuttings and start of some seedlings. 

I hate DIY and the thought of buying in all the bits...so I've been researching - I've come across the HOTBOX Heatwave mats. It's a complete set up and probably a less fuss option for me.
You buy the heatmat the size of your requirements and they supply the thermostat.
You put it on your bench on top of a thick layer of polystyrene, plastic/pond liners? on top and then a layer of capillary matting. Plug it in and away to go.

I like the simplicity of it. I'm very much tempted even though I should be spending my pennies on a kitchen sink.