There are other ways to stop user connections to SQL Server except for denying logins. Since the restore time will not be long as you sais the DB is not big, you can:
1.Unplug the network cable and work locally
2. Do not unplug the network cable. Go to SQL Server's Server Network Utility (2000) or SQL Server Configuration Manager (2005) and temp. disable the TCP/IP and Named Pipes. Leave just Shared Memory. Log in to the server using Terminal Services and work with SQL Server locally.
3. Do not unplug the network cable. Do not disable protocols. Change the listening port on the server and create an alias for this port on your client. Work remotely.