Oh boy are we going to have fun on here tonight then...
I had the same knock back in November. I normally send them away as, like you, I'm not on benefits so I don't qualify either. This time I listened, and long story short I managed to get all my loft insulation re-done and all my cavity walls filled, for free! Basically they've run out of people on benefits to give this too, so they're now offering it to everyone as they've still got the funds from government to spend. On top of this, because I've now had this done when they come round with free boilers I automatically qualify for that too!
I think this country is ace. People like me who work their arse off get free stuff. Love it.