OK, I figured it out eventually - Port 137 has to be enabled on Server 2

The only port request showing on my firewall log is 1433

I use Neorouter to create a VPN for this, easy to setup and free to home users.

Normalisation may be a disadvantage when Warehousing data which is going to be read-only.

Sorted - I remembered that when you are running a 64 bit version, you still have to set the alias up under 32 bit; I would have expected that sort...