Assuming it's a Quest1, not sure about Q2 as that uses different mapping technology.
Yep, if you usually have the whole of the UK on your Quest just select "City Nav v8" from the drop down.
1/ Then zoom out until you can see the whole of the UK.
2/ Then click the maps tab in the left pane.
3/ Click the 'map tool' (tool bar button to left of the magnifying glass)
4/ Then select the map tiles you want by just clicking or clicking and dragging (they should turn pink as you do this).
5/ As you add tiles you will see them appear by name in the left 'Maps' pane, at the bottom of this pane you'll see a total file size, you can add maps to a total of 243MB, the European Quest1 won't hold more than this.
6/ Connect your Quest and select 'Transfer' > 'Send to Device' from the menus, opt to send maps and click the 'Send' button. Expect it to take 20 minutes to transfer.
N.B. Uploading maps removes all previous maps uploaded so if you have the speed camera overlay you'll need to add that at step 4 as well. The UK one is only around 1MB, select the overlay in the drop down menu and highlight the UK overlay, currently the French one that seems to be included only has one or two cameras on it
BTW, if you're planning any long trips CN v8 uses 2 to 3 times the memory compared to v6 which will severely limit your range within Europe. You'll either need to use v6, take a laptop or rely on the basemap for part of your journey. This is down to the far bigger tile size which neatly torpedoes the usability of the Quest for European touring, maybe Garmin would all like us to buy Zumos
I've asked them if they've realised this 'mistake' to which they, in essence, have replied 'that's the way it is, take it or leave it'.
there must be a simple answer 
