yes mate its a bit naughty but unfortunately free mapping is but a dream with sat nav manufacturers as once they,ve sold you the unit they continue to make money from mapping upgrades
People sell the maps for many different Sat Nav's on eBay, you could try there, they'll be cheaper than going to the say Tom Tom etc, but is still illegal.
google earth is free... but the pure amount of data that needs transferring for the images would cripple a mobile devicew... there simply isnm't enough RAM