Although with IP telephony , allocation of a directory number outside its normal ‘area’ is not a technical issue , the linked number scheme where the ( in general ) the STD code indicates the town/city and the next numbers the individual exchange ( and therefore the suburb ) , so 01234 567111 and 01234 456111 could be separate exchanges ( 56 and 45 ) within the same town , and it wouldn’t be possible for a home mover to take a 56 number into the 45 exchange area , even if they were neighbouring areas .
AFAIK, the Linked Number Scheme LNS ( so your telephone number indicates the general geographical location ) is still valued……I’ve never seen confirmation that this desirable link between a phone number and geographic area has been abandoned, and it’s now effectively a free for all when it comes to number allocation, the police for one were keen to see it maintained, plus if it’s possible to move a number in a small scale way ( so the STD code doesn’t change but you can have a 56 number in the 45 exchange area ) why not be able to have a Manchester number in Newcastle .
It may well be the BT guide was correct and you can’t take your number across the old PSTN exchange boundary, even if it’s technically uncomplicated, it may simply be undesirable and still denied to anyone asking for it .
I can’t be certain so ( with the appropriate citation ) I’d accept that the LNS is longer maintained, but I’ve not seem any evidence of this ( short of incompetence of some LLU operators ) , and obviously this is relevant only to a home mover staying on the same network , isn’t the same as number portability
