Re: £35 / user?
MS A1 accounts are OK if you don't actually need anything like, y'know, actual real apps (Outlook, Word, Excel, etc). The web-based apps are kinda fun and OK for the basics, but good luck there if all your file data and storage is on-prem for reasons.
Microsoft has *two* separate computing environments, on-prem (old) and cloud (new), and mixing them is at the least just a new kind of Hell, and at worst is not actually possible or reliable (Onedrive or Teams on RDS, anyone?)
A/C because I'm not admitting to using this stuff in a public forum.