Bev Nicolson asked:
With VM, I needed to be taken through registration via their IP address (yes, some support for Linux!) but will I need to go through something like that again when I swop the way I get broadband?
It depends on the provider, but many of them just give you router or modem settings these days. Check the provider's website's support/setup section to try to find out before you order.
http://sod.ms/ are very strong pro-Linux and solve some problem cases, while our partner's http://www.software.coop/phone really shouldn't cause any problems either (worksforme).
Hope that helps,