you may or may not already be aware of this but for all those lucky souls with a blackberry you can download sat nav for free! its a vodaphone app but will work on your handset regardless of your network - my phones locked to orange and its ok. good little program with maps, direction list and verbal + onscreen step by step instructions. no camers alerts though. I've lost the link I was going to post so will return with it later but a bit of googleing should see you finding it though.
I got a Blackberry with that Satnav (im on Vodaphone), but my brother is on O2 and downloaded that Satnav, and got charged a small amount for connection and kb used.