That's not quite true. The Crown would have to prove that you had either obstructed the investigation (in which case the crime would be perverting the course of justice) or you have deliberately disobeyed a court order from a previous court hearing, in which case you could be jailed but I am unaware of a judge deciding that you can be jailed just because they don't believe you.

Disclaimer: UK resident who is NOT qualified in law ;-)