Thanks for the replies - I'm not using Unity Analytics, IAP or Multiplayer services.
When I start up a build of my game my Anti-virus is picking up a request out to Unity's cloud servers.
As far as I can tell this is linked to the "Disable HW Statistics" check box in Unity Editor's Player Settings - which is unfortunately unchangeable in Personal Edition.
The request seems to be made as the application is loading so I'm not really sure at what point I'd be able to show a button.
Good news though!
Looks like in newer versions of the editor it can actually be disabled even in Personal Edition:
https://forum.unity.com/threads/does-disable-hw-statistics-option-also-disable-analytics.627274/