Martins Money Saving Tips had a recomendation on last weeks update for Navmii, a free of charge Sat Nav.
Its free of charge to download, Ive used it three times and its very very good...........Ive subsequently paid the grand sum of £1.49 to remove pop up adverts.
They also do a Spanish version which I will be downloading before our next visit, saves packing the sat nav ;-)
Using the sat nav doesnt use any of your data allowance, its FOC.
Regards all
John