Thanks both. Looks like I need this:
2.12 Prevent the visual selection overriding my system clipboard?
On some operating systems, there is only one clipboard for both copied and selected texts. This has the consequence that visual selection – which should normally be saved to the PRIMARY clipboard – overrides the SYSTEM clipboard, where normally goes the copied text. This can be corrected by adding the following code to the dotspacemacs/user-config of your .spacemacs:
(fset 'evil-visual-update-x-selection 'ignore)
