On single person frauds

A commenter puts it well

It's easy because the D.W.P. simply pay out income support to anyone "single parent" who wants it. They then continue to have children and see their benefits increase. Very few questions or checks appear to be done.

A woman with young kids will not get a prison sentence; she'll continue to get benefits with a small deduction towards the overpayment.

So heads you win; if you're very unlucky and you get caught ... tails - well, you scarcely lose.