Switch maps in Navigator5 on Mio A201

I've got TomTom Navigator 5 on my Mio A201. I've switched maps before (from GB to France and Italy) but haven't done it for a while. I'm off to France next week and so in preparation tried to switch to my French maps last night. But I don't seem to be able to see them when I select Switch maps from Change preferences.

The maps are definitely on the SD card and the SD card is definitely inserted. I seem to recall seeing something about needing to delete a file somewhere before, but can't remember it as I've not had the issue before/not used it other than for GB for ages.

I'm sure someone here will be able to help

Seems a soft reset solved the issue, don't know why I didn't think about that in the first place!