but will be more than 2

If you only have two sites, you probably do NOT need to book a bridge. You can simply call from one site to another.

NHS Scotland or Scottish Govt systems should call each other on their standard 9-digit VC numbers.

Scottish Govt systems VC numbers are derived from their ISDN numbers by simply putting 610 in place of 01312. e.g. 0131 242 1234 would be 610412234.