you might want to check out this web site before fitting any bull bars.
http://www.frontalprotectionsystems.eu/ ... gister.php
They have loads of information about if it is legal or not to have bull bars, the government are having a consultation at the momemnt on bull bar legislation and there is a down load for the presentation they gave at the stakeholders meeting which states that it is illegal to sell them, and that under the road traffic act, the driver may be committing an offence if the vehicle is fitted with a non approved frontal protection system.
The consultation will be on this web site when the DfT get around to psoting it.

http://www.dft.gov.uk/consultations/open/?w=dft