OpenStreetMap, what’s the latest….

Not 100% on this but from what i can remember and its been a while since i used OSM on my 660, you can have the naming format as below. this is with latest firmware

Zumo
Internal memory 4 IMGs are supported
gmapprom.img
gmapprom1.img
gmapsupp.img
gmapoem.img
SD just one gmapsupp.img is supported
gmapsupp.img

i just carried a couple of spare sd cards and changed when needed, its a 2 minute job.

OK. All sorted now!
For future reference, the issue is indeed to do with the file name. I had thought that all would be well as long as the name contained gmapsupp. Not so. The name is restricted to Gmapsupp (as suggested by Lee above) and that's it! Hence only one map set is possible. All I had to do was download the file, remove the name of the country and transfer it to the card and bingo, it worked!

A point to note is that, while the country may be missing from the file name, the unit will still display the country name, as in the pic below.

Thanks for all the suggestions. Henceforward you may call me Mr Thickie, then cover me in honey and throw me to the lesbians!

Glad you got it sorted.

Thanks from me too folks.
I must have tried to get this sorted for hours over the last few year. ###
Cheers Thicko Micko

New to this forum, and looking for GPS related info, I came across this thread.

I used to do a lot of Geocaching with a Garmin etrex legend, and always got maps from here...

It looks like his maps work on Zumo XTs but I cannot confirm. Hope this is helpful.