Maybe it's time for you to contact Garmin UK support about this. Regardless of whether a device is or isn't LM, on the 'Device Content' tab of the Map Update page it should at least show you the OEM detail mapping factory-loaded [see post #8] even if there has been no other official updates done since it was purchased. This is an AU 3790 non-LM which has never been updated:

[Only registered and activated users can see links. ]

But it still shows the OEM map details. Once updated it will still show the map and Product key as in Post #8 pics.