Have Win 10 Pro & Home licences. Can I use them on Surface Laptop Go?

There is no need to use one of the spare 10 digital licences. The change from S Mode is free
Be aware you CANNOT go back from Windows 10 Home to S Mode
Although it should be trouble free and presuming the Surface Laptop will not have any personal data on it, be aware that if it does go wrong - a system image would be a wise precaution - if when you make the switch there is personal data and apps

Although as I said there is no need to use a licence as the switch is free you may indeed NOT be able to use one of those licences.
If you upgrade a Windows 7 Home or Pro - OEM to 10 then your digital activation is still an OEM and therefore if it is a OEM SLP it is locked to the hardware hash that was registered on the microsoft servers. It therefore cannot be used on a completely different device.
New hardware is allowed as per here
https://support.microsoft.com/en-us/...d-fb3fc72b6665

but that is meant to replace a motherboard or CPU - hardware changes such as a disk do not require reactivation.
However it is not meant to allow - a complete new device.

If however the 7 install was retail then YES it can be used on any device, but of course ONLY on one at anytime.

To change Home S to Home see this
https://support.microsoft.com/en-us/...f-031bfb28a307

and the tutorial from Brink
Switch out of S mode in Windows 10 for Free

finnfire
You having seen my advice - your response would be greatly appreciated

Cheers
I was just concerned you may have missed the notification of my reply,.
Hope it works out for you.,