Thread: Nuvi55/56/65/66/25x9/26x9,zûmo590,GPSMAP64,Edge1000 cant authenticate map error

Hello,
I am leaving to UK (London area) this weekend and I was given a brand new Nuvi 55 (firmware 4.50) with maps "CN North America NT 2016.20". I am totally new to Garmin as I previously used iGO Worldwide (where adding a map was a matter of uploading a correct file onto device). Is there any chance to install a UK map onto this Nuvi?
I am aware of this topic:
[Only registered and activated users can see links. ]
but I have no idea which map would be accepted by device.

P.S. I am traveling quite often all over the world, so a way to upload maps of any country would be very much appreciated. Also I have only 2GB SD Card, so some files simply won't fit there.