well, update,
I plugged in the nav 5 again and garmin express says all maps up to date etc, still with all north installed and no south.
so I went into basecamp and then into the map updater,
I still cant find any reference anywhere to install Europe south, it just lists full Europe,
I formatted my sd card to fat 32 yet again removing all of the full Europe maps installed on it.
anyway after checking which countries are installed in the Europe north I went into custom installation and selected all of the countries in the south that are not in the Europe north file,
this came out at about 3.5 meg of data, clicked to install and left it for a few hours, came back a few hours later, message saying all installed successfully.
removed the nav 5 from the computer, crossed my fingers etc,
turned it on,
says maps uploading as before.
this time it carried on and started up fine, no shutting down as it was starting up.
I now have mapping in France Spain Italy and Croatia Serbia and all the surrounding countries, zoomed in on many towns and have all of the streets and names there, did a search and all of the countries come up to search for an address.
I still cant understand why I cant find the option to install all of south, to go with the north installed but at least it now has what I require to travel to France at the end of may.
maybe I do need to purge the computer of stuff that I used to use for my old zumo 550, it could be causing issues, no idea how to do it though.
oh well at least its worked to a certain extent,
thanks for your help and I hope this may help others to get theirs working.
I wiped all Garmin files from my pc (windows 10) and now have Europe 2018.10 on my pc and have just made maps from Calais to Mugello and all is fine.
However, I still cannot find where they are stored on my pc (and I've unhidden all folders / files) in order to copy to my Nav V which, like yours, will only accept North.
F****** software!!!!!!!!!!!!!!!!!!!!!!!!!!!!