Free insulation scam?

Sergipot

Hi everyone, I'm quite worried about something that happened today.
So a guy showed up on my door, and explained me that the government was paying to fix the isolation in the lofts, so that would be free for me.
They explained after checking my loft, that I had 100mm and 300mm was the required in the 2020 schedule, so they can do it for free.
I accepted and they have done everything for free, but I was at work at the moment and I didn't think it properly as I was very busy. 
Can this be a scam? How can it be a scam if they've done all the job and haven't charged me at all?
Please let me know what you think.
Many thanks, 

ABrass

Did you sign anything?

Sergipot

I signed a paper that said the installers finished a few things in the loft and another paper of the location of the house.
But I didn't sign any contract or anything like that. The first paper I signed an option that said the government would pay for it?

Scrapper

We had a scam phone call from someone wanting to give us a grant for loft insulation. We gave him pretty short shrift. We thought he was going to ask us for bank details or something like that so he could transfer some money to us. I wish we'd strung him along now to see what the scam involved.

It's quite fun wasting as much of these scammers' time as possible. Can you hang on a moment the postman's at the door, got to let the dog in, let me go and get my bank details (not really obviously!). It's quite fun if you're in the right sort of mood.