Howdy @M_Titcombe!
Thank you for your interest in reselling M365 GCC High. Currently customers can purchase M365 GCC High via Enterprise Agreement (EA) that are available for customers with 500 employees or larger. There are eleven Licensing Solutions Partners that offer EAs in the US. Customers that are smaller than 500 employees can purchase via Agreement for Online Services Government (AOS-G) partners. There are eleven Licensing Solutions Partners that offer EAs in the US. There are nine AOS-G partners today. AOS-G was initially set up as a temporary "stop-gap" licensing vehicle to serve sub-500 customers until Microsoft can make M365 GCC High available via Cloud Service Provider (CSP) agreements. Bottom line, Microsoft is working hard to build the supporting infrastructure to enable M365 GCC High via CSP as soon as possible to scale out the ability of qualified partners to be able to resell to their customers.
I hope this helps!
