"The kind of car crash that mounts the kerb, destroys the barrier and ends up in your living room"
Exactly, and the driver then gets discredited and banged in jail (unless he's Andrew Flintoff of course). That is the thing with UKIP, the dilemma they face: their huge attraction for a lot of people is that they carry no baggage of previous tried and failed policies. That attraction can either remain one - without any power - or it can quickly disappear, and in UKIP's case I suspect it would be very quick.