Scam or not scam?

I got an email, offering a refund of £300-odd on car insurance. All I had to do, was give them my bank account number, sort code and suchlike.

What?

But they also had in the email, the registration number of the car we sold a while back, so the refund was for that. That made me think that maybe, just maybe, this isn't actually a scam.

So I called our insurers. And it wasn't a scam, it was genuine.

So I gave them the rough side of my tongue on the issue of sending out emails asking for bank details. Apparently, lots of other people, including their internal departments, have told them the same thing.

They're going to send me a cheque.