A Problem With The Windows Scrappage Scheme?

It occurred to me while thinking of all the good that the scrappage scheme may bring, there could be one big problem with it. How would it be organised and policed?

It was easy with the car scrappage scheme as the DVLA have paperwork on every car on the road in the UK. So they would know when an old car was going in for scrap. How would the organisation running our scrappage scheme know when an old windows installation is being removed?

I think the most evident way would be to get FENSA involved and have them police the system. They already register all the new installations so there would be nothing new to do there. They would however have to inspect every old windows installation that comes out of a house, and then inspect the new installation when it is complete. The number of man-hours would dramatically increase, but could it also create jobs too? One thing I suspect would happen if FENSA were to police the scheme would be that they would charge for this service, and it wouldn't be a small sum either. Let me know if any of you think of any other ways, but to me this seems like the easiest and most readily available method to hand so far.