If you have had the same phone number for 36 years, and the cable industry Telco provided that number initially , rather than it being a BT number ported to cable, you must have been one of the very earliest cable company customers, if you had ‘cable’ in 1986, when the cable industry didn’t really get going until the early to mid 1990’s.
Number portability is the arrangement that allows someone changing provider to keep the phone number at their current address , it’s not a mechanism to take a number with you to a new address.
If you have moved address and are hoping to take the number with you , but are also changing provider , then it’s likely that it will fail, technically that isn’t a number port request , as the addresses are different, the address the VF service was at is different to the address you want BT service at.
If you were not also changing provider and were simply moving address with BT , and both the old and new address were within the same ‘exchange’ area then that would be a ‘home mover’ service you needed ( not a number port ) and it would be possible to keep the same number but , although 1.5miles isn’t a particular large distance, it could still be enough of a distance that the addresses are not from the same exchange, you couldn’t move the number , if it were the same exchange you don’t qualify as you are changing provider, if you are going to be DV that adds in another level of complexity.
Lastly , there aren’t any areas where BT are the only choice , if BT are available then others are available too, BT use Openreach , and Openreach are available to any Telco that wants to use them, a few years ago the well known competitor brands didn’t bother with OR FTTP ( that was their choice , they could have offered service if they wanted to ) but these days even those brands offer FTTP over OR now, and even back then , there were alternatives to BT
