The rules regarding number plates are still in effect and breaching of them can result in a £1,000 fine and an MoT failure. You can read the exact specifications required here: www.gov.uk/displaying-number-plates/rules-number-p...s

There are no statistics available for the frequency of penalties issued for illegal number plates, so it is difficult to tell whether the increase in the use of illegal number plates has resulted in an increase in penalties. Ultimately it is a matter for the police who have to decide how to deploy their resources.