I have a Nuvi 1310 preloaded with UK and Ireland maps. As I'm off to France, I bought a Benelux + France City Navigator sd card but I see the booklet says the map data will overwrite pre-programmed maps. So does this mean if I inswrt the France sd card, I will lose my UK maps? I thought i could run the 2 together, is there any way to do this or have I got it wrong?