I am looking to restrict the access of a particular user to be from one
server only without affecting the access of other users.

I cannot think of an AllowUsers way of doing this.

The only way I can think of is by using DenyUsers which will be
unwieldy as in practice I have a lot of users and a lot of subnets.
This would only take me down to subnet level without an even longer
line.

DenyUsers user1@\m172.0/8,user1@\m10.0/8 etc etc etc

Any ideas? I am using Reflection (F-Secure) SSH 6.1.

Thanks,
Nick