As its not a legal requirement to be insured, (and this is not assault-it is an accident), I don't think you'd face prison.
But this would almost certainly mean bankruptcy.
That would not help the victim much though, after bankruptcy expenses, you would be left with at most a few thousand pounds once the estate had been liquidated.
I hate to think that I could be a victim of an accident by an uninsured driver, tradesman etc and I'd get no compensation. I don't want to put other people in that position, so I get insured.
Philip