Re: Windfalls
That sounds about right.
IANAL but I understand that UK law is along the lines of, "you can't keep it if it was obviously an error".
So for example if a company accidentally sends you a big sum of prize money you can keep it because you might legitimately think you'd won their prize draw.
On the other hand if it mysteriously appears in your account for no apparent reason then you can't keep it because you well know it isn't yours.