I've been trying to update my TomTom GO 700 to the 1015 maps (or really anything remotely recent - it was bought ~2005 and had never been updated ever!).
I used the TomTom HOME app to update the navcore to 7.903, which I beleive is the latest that can run on the GO 700.
I then saw that maps 1015 support navcore 7.903, so I downloaded Western Europe 1GB 1015 9156 which left me with ...