Hello @Douglas Bowman | Swap-Ict ,
Thank you for reaching out to Microsoft Q&A platform. Happy to answer your question.
If you are looking at the below highlighted Azure Virtual Desktop under Microsoft 365 Business Premium plan, it means that you can license your azure virtual desktops using Microsoft 365 Business Premium account, but still you would need an azure subscription seperately in order to create the AVDs. Please refer to Azure Virtual Desktop Overview
microsoft-365-business-premium
From the AVD document:
Also take a look at the pricing document of AVD, to understanding the licensing concept combining with Microsoft 365 business here, virtual-desktop
Please "Accept as Answer" and Upvote if any of above helped so that, it can help others in community looking for remediation for the similar issues