Moving office & static IP addresses

[#1]

Is there anything special to take into account when moving our ADSL connection to a new line (on a different BT exchange) so we don't loose our existing block of static IP addresses?
The same also applies to our fax-to-email number?

[#2]

Both are attached to your username, Username (ho ho!).
Your account would remain active throughout, so you would keep both.