If your phone is in a cradle then you may use it as a navigation aid, but pressing buttons or holding the phone while driving is illegal. It is, however, legal to make and receive calls/send voice texts using a hands-free system. Basically, all new cars come with Bluetooth systems fitted as standard, which allows the driver to use their phone legally. Although, even when using a legal hands-free kit, drivers can still be charged with careless driving, dangerous driving or driving without due care and attention if the police believe that it affected their standard of driving.